Running the Persistence Examples

We are working on a fresh, updated Jakarta EE Tutorial. This section hasn’t yet been updated.

This chapter explains how to use Jakarta Persistence. The material here focuses on the source code and settings of three examples.

Overview of the Persistence Examples

The first example, order, is an application that uses a stateful session bean to manage entities related to an ordering system. The second example, roster, is an application that manages a community sports system. The third example, address-book, is a web application that stores contact data. This chapter assumes that you are familiar with the concepts detailed in Introduction to Jakarta Persistence.

The order Application

The order application is a simple inventory and ordering application for maintaining a catalog of parts and placing an itemized order of those parts. The application has entities that represent parts, vendors, orders, and line items. These entities are accessed using a stateful session bean that holds the business logic of the application. A simple singleton session bean creates the initial entities on application deployment. A Facelets web application manipulates the data and displays data from the catalog.

The information contained in an order can be divided into elements. What is the order number? What parts are included in the order? What parts make up that part? Who makes the part? What are the specifications for the part? Are there any schematics for the part? The order application is a simplified version of an ordering system that has all these elements.

The order application consists of a single WAR module that includes the enterprise bean classes, the entities, the support classes, and the Facelets XHTML and class files.

The database schema in the Derby database for order is shown in Figure 1, “Database Schema for the order Application”.

Diagram showing the database schema for the order application

Figure 1. Database Schema for the order Application

In this diagram, for simplicity, the PERSISTENCE_ORDER_ prefix is omitted from the table names.

Entity Relationships in the order Application

The order application demonstrates several types of entity relationships: self-referential, one-to-one, one-to-many, many-to-one, and unidirectional relationships.

Self-Referential Relationships

A self-referential relationship occurs between relationship fields in the same entity. Part has a field, bomPart, which has a one-to-many relationship with the field parts, which is also in Part. That is, a part can be made up of many parts, and each of those parts has exactly one bill-of-material part.

The primary key for Part is a compound primary key, a combination of the partNumber and revision fields. This key is mapped to the PARTNUMBER and REVISION columns in the PERSISTENCE_ORDER_PART table:

...
@ManyToOne
@JoinColumns({
    @JoinColumn(name="BOMPARTNUMBER", referencedColumnName="PARTNUMBER"),
    @JoinColumn(name="BOMREVISION", referencedColumnName="REVISION")
})
public Part getBomPart() {
    return bomPart;
}
...
@OneToMany(mappedBy="bomPart")
public Collection<Part> getParts() {
    return parts;
}
...

One-to-One Relationships

Part has a field, vendorPart, that has a one-to-one relationship with VendorPart's part field. That is, each part has exactly one vendor part, and vice versa.

Here is the relationship mapping in Part:

@OneToOne(mappedBy="part")
public VendorPart getVendorPart() {
    return vendorPart;
}

Here is the relationship mapping in VendorPart:

@OneToOne
@JoinColumns({
    @JoinColumn(name="PARTNUMBER", referencedColumnName="PARTNUMBER"),
    @JoinColumn(name="PARTREVISION", referencedColumnName="REVISION")
})
public Part getPart() {
    return part;
}

Note that, because Part uses a compound primary key, the @JoinColumns annotation is used to map the columns in the PERSISTENCE_ORDER_VENDOR_PART table to the columns in PERSISTENCE_ORDER_PART. The PERSISTENCE_ORDER_VENDOR_PART table’s PARTREVISION column refers to PERSISTENCE_ORDER_PART's REVISION column.

One-to-Many Relationship Mapped to Overlapping Primary and Foreign Keys

CustomerOrder has a field, lineItems, that has a one-to-many relationship with LineItem's field customerOrder. That is, each order has one or more line item.

LineItem uses a compound primary key that is made up of the orderId and itemId fields. This compound primary key maps to the ORDERID and ITEMID columns in the PERSISTENCE_ORDER_LINEITEM table. ORDERID is a foreign key to the ORDERID column in the PERSISTENCE_ORDER_CUSTOMERORDER table. This means that the ORDERID column is mapped twice: once as a primary key field, orderId; and again as a relationship field, order.

Here is the relationship mapping in CustomerOrder:

@OneToMany(cascade=ALL, mappedBy="customerOrder")
public Collection<LineItem> getLineItems() {
    return lineItems;
}

Here is the relationship mapping in LineItem:

@Id
@ManyToOne
@JoinColumn(name="ORDERID")
public CustomerOrder getCustomerOrder() {
    return customerOrder;
}

Unidirectional Relationships

LineItem has a field, vendorPart, that has a unidirectional many-to-one relationship with VendorPart. That is, there is no field in the target entity in this relationship:

@JoinColumn(name="VENDORPARTNUMBER")
@ManyToOne
public VendorPart getVendorPart() {
    return vendorPart;
}

Primary Keys in the order Application

The order application uses several types of primary keys: single-valued primary keys, generated primary keys, and compound primary keys.

Generated Primary Keys

VendorPart uses a generated primary key value. That is, the application does not assign primary key values for the entities but instead relies on the persistence provider to generate the primary key values. The @GeneratedValue annotation is used to specify that an entity will use a generated primary key.

In VendorPart, the following code specifies the settings for generating primary key values:

@TableGenerator(
    name="vendorPartGen",
    table="PERSISTENCE_ORDER_SEQUENCE_GENERATOR",
    pkColumnName="GEN_KEY",
    valueColumnName="GEN_VALUE",
    pkColumnValue="VENDOR_PART_ID",
    allocationSize=10)
@Id
@GeneratedValue(strategy=GenerationType.TABLE, generator="vendorPartGen")
public Long getVendorPartNumber() {
    return vendorPartNumber;
}

The @TableGenerator annotation is used in conjunction with @GeneratedValue's strategy=TABLE element. That is, the strategy used to generate the primary keys is to use a table in the database. The @TableGenerator annotation is used to configure the settings for the generator table. The name element sets the name of the generator, which is vendorPartGen in VendorPart.

The PERSISTENCE_ORDER_SEQUENCE_GENERATOR table, whose two columns are GEN_KEY and GEN_VALUE, will store the generated primary key values. This table could be used to generate other entities' primary keys, so the pkColumnValue element is set to VENDOR_PART_ID to distinguish this entity’s generated primary keys from other entities' generated primary keys. The allocationSize element specifies the amount to increment when allocating primary key values. In this case, each VendorPart's primary key will increment by 10.

The primary key field vendorPartNumber is of type Long, as the generated primary key’s field must be an integral type.

Compound Primary Keys

A compound primary key is made up of multiple fields and follows the requirements described in Primary Keys in Entities. To use a compound primary key, you must create a wrapper class.

In order, two entities use compound primary keys: Part and LineItem.

Part uses the PartKey wrapper class. Part's primary key is a combination of the part number and the revision number. PartKey encapsulates this primary key.
LineItem uses the LineItemKey class. LineItem's primary key is a combination of the order number and the item number. LineItemKey encapsulates this primary key.

This is the LineItemKey compound primary key wrapper class:

package ee.jakarta.tutorial.order.entity;

import java.io.Serializable;

public final class LineItemKey implements Serializable {

    private Integer customerOrder;
    private int itemId;

    public LineItemKey() {}

    public LineItemKey(Integer order, int itemId) {
        this.setCustomerOrder(order);
        this.setItemId(itemId);
    }

    @Override
    public int hashCode() {
        return ((this.getCustomerOrder() == null
                ? 0 : this.getCustomerOrder().hashCode())
                ^ ((int) this.getItemId()));
    }

    @Override
    public boolean equals(Object otherOb) {
        if (this == otherOb) {
            return true;
        }
        if (!(otherOb instanceof LineItemKey)) {
            return false;
        }
        LineItemKey other = (LineItemKey) otherOb;
        return ((this.getCustomerOrder() == null
                ? other.getCustomerOrder == null : this.getOrderId()
                .equals(other.getCustomerOrder()))
                && (this.getItemId == oother.getItemId()));
    }

    @Override
    public String toString() {
        return "" + getCustomerOrder() + "-" + getItemId();
    }

    public Integer getCustomerOrder() {
        return customerOrder;
    }

    public void setCustomerOrder(Integer order) {
        this.customerOrder = order;
    }

    public int getItemId() {
        return itemId;
    }

    public void setItemId(int itemId) {
        this.itemId = itemId;
    }
}

The @IdClass annotation is used to specify the primary key class in the entity class. In LineItem, @IdClass is used as follows:

@IdClass(LineItemKey.class)
@Entity
...
public class LineItem implements Serializable {
    ...
}

The two fields in LineItem are tagged with the @Id annotation to mark those fields as part of the compound primary key:

@Id
public int getItemId() {
    return itemId;
}
...
@Id
@ManyToOne
@JoinColumn(name="ORDERID")
public CustomerOrder getCustomerOrder() {
    return customerOrder;
}

For customerOrder, you also use the @JoinColumn annotation to specify the column name in the table and that this column is an overlapping foreign key pointing at the PERSISTENCE_ORDER_CUSTOMERORDER table’s ORDERID column (see One-to-Many Relationship Mapped to Overlapping Primary and Foreign Keys). That is, customerOrder will be set by the CustomerOrder entity.

In LineItem's constructor, the line item number (LineItem.itemId) is set using the CustomerOrder.getNextId method:

public LineItem(CustomerOrder order, int quantity, VendorPart vendorPart) {
    this.customerOrder = order;
    this.itemId = order.getNextId();
    this.quantity = quantity;
    this.vendorPart = vendorPart;
}

CustomerOrder.getNextId counts the number of current line items, adds 1, and returns that number:

@Transient
public int getNextId() {
    return this.lineItems.size() + 1;
}

Part requires the @Column annotation on the two fields that comprise Part's compound primary key, because Part's compound primary key is an overlapping primary key/foreign key:

@IdClass(PartKey.class)
@Entity
...
public class Part implements Serializable {
    ...
    @Id
    @Column(nullable=false)
    public String getPartNumber() {
        return partNumber;
    }
    ...
    @Id
    @Column(nullable=false)
    public int getRevision() {
        return revision;
    }
    ...
}

Entity Mapped to More Than One Database Table

Part's fields map to more than one database table: PERSISTENCE_ORDER_PART and PERSISTENCE_ORDER_PART_DETAIL. The PERSISTENCE_ORDER_PART_DETAIL table holds the specification and schematics for the part. The @SecondaryTable annotation is used to specify the secondary table:

...
@Entity
@Table(name="PERSISTENCE_ORDER_PART")
@SecondaryTable(name="PERSISTENCE_ORDER_PART_DETAIL", pkJoinColumns={
    @PrimaryKeyJoinColumn(name="PARTNUMBER",
        referencedColumnName="PARTNUMBER"),
    @PrimaryKeyJoinColumn(name="REVISION",
        referencedColumnName="REVISION")
})
public class Part implements Serializable {
    ...
}

PERSISTENCE_ORDER_PART_DETAIL and PERSISTENCE_ORDER_PART share the same primary key values. The pkJoinColumns element of @SecondaryTable is used to specify that PERSISTENCE_ORDER_PART_DETAIL's primary key columns are foreign keys to PERSISTENCE_ORDER_PART. The @PrimaryKeyJoinColumn annotation sets the primary key column names and specifies which column in the primary table the column refers to. In this case, the primary key column names for both PERSISTENCE_ORDER_PART_DETAIL and PERSISTENCE_ORDER_PART are the same: PARTNUMBER and REVISION, respectively.

Cascade Operations in the order Application

Entities that have relationships to other entities often have dependencies on the existence of the other entity in the relationship. For example, a line item is part of an order; if the order is deleted, then the line item also should be deleted. This is called a cascade delete relationship.

In order, there are two cascade delete dependencies in the entity relationships. If the CustomerOrder to which a LineItem is related is deleted, the LineItem also should be deleted. If the Vendor to which a VendorPart is related is deleted, the VendorPart also should be deleted.

You specify the cascade operations for entity relationships by setting the cascade element in the inverse (nonowning) side of the relationship. The cascade element is set to ALL in the case of CustomerOrder.lineItems. This means that all persistence operations (deletes, updates, and so on) are cascaded from orders to line items.

Here is the relationship mapping in CustomerOrder:

@OneToMany(cascade=ALL, mappedBy="customerOrder")
public Collection<LineItem> getLineItems() {
    return lineItems;
}

Here is the relationship mapping in LineItem:

@Id
@ManyToOne
@JoinColumn(name="ORDERID")
public CustomerOrder getCustomerOrder() {
    return customerOrder;
}

BLOB and CLOB Database Types in the order Application

The PARTDETAIL table in the database has a column, DRAWING, of type BLOB. BLOB stands for binary large objects, which are used for storing binary data, such as an image. The DRAWING column is mapped to the field Part.drawing of type java.io.Serializable. The @Lob annotation is used to denote that the field is a large object:

@Column(table="PERSISTENCE_ORDER_PART_DETAIL")
@Lob
public Serializable getDrawing() {
    return drawing;
}

PERSISTENCE_ORDER_PART_DETAIL also has a column, SPECIFICATION, of type CLOB. CLOB stands for character large objects, which are used to store string data too large to be stored in a VARCHAR column. SPECIFICATION is mapped to the field Part.specification of type java.lang.String. The @Lob annotation is also used here to denote that the field is a large object:

@Column(table="PERSISTENCE_ORDER_PART_DETAIL")
@Lob
public String getSpecification() {
    return specification;
}

Both of these fields use the @Column annotation and set the table element to the secondary table.

Temporal Types in the order Application

The CustomerOrder.lastUpdate persistent property, which is of type java.util.Date, is mapped to the PERSISTENCE_ORDER_CUSTOMERORDER.LASTUPDATE database field, which is of the SQL type TIMESTAMP. To ensure the proper mapping between these types, you must use the @Temporal annotation with the proper temporal type specified in @Temporal's element. @Temporal's elements are of type jakarta.persistence.TemporalType. The possible values are

DATE, which maps to java.sql.Date
TIME, which maps to java.sql.Time
TIMESTAMP, which maps to java.sql.Timestamp

Here is the relevant section of CustomerOrder:

@Temporal(TIMESTAMP)
public Date getLastUpdate() {
    return lastUpdate;
}

Managing the order Application’s Entities

The RequestBean stateful session bean contains the business logic and manages the entities of order. RequestBean uses the @PersistenceContext annotation to retrieve an entity manager instance, which is used to manage order's entities in RequestBean's business methods:

@PersistenceContext
private EntityManager em;

This EntityManager instance is a container-managed entity manager, so the container takes care of all the transactions involved in managing order's entities.

Creating Entities

The RequestBean.createPart business method creates a new Part entity. The EntityManager.persist method is used to persist the newly created entity to the database:

Part part = new Part(partNumber,
        revision,
        description,
        revisionDate,
        specification,
        drawing);
em.persist(part);

The ConfigBean singleton session bean is used to initialize the data in order. ConfigBean is annotated with @Startup, which indicates that the enterprise bean container should create ConfigBean when order is deployed. The createData method is annotated with @PostConstruct and creates the initial entities used by order by calling RequestBean's business methods.

Finding Entities

The RequestBean.getOrderPrice business method returns the price of a given order based on the orderId. The EntityManager.find method is used to retrieve the entity from the database:

CustomerOrder order = em.find(CustomerOrder.class, orderId);

The first argument of EntityManager.find is the entity class, and the second is the primary key.

Setting Entity Relationships

The RequestBean.createVendorPart business method creates a VendorPart associated with a particular Vendor. The EntityManager.persist method is used to persist the newly created VendorPart entity to the database, and the VendorPart.setVendor and Vendor.setVendorPart methods are used to associate the VendorPart with the Vendor:

PartKey pkey = new PartKey();
pkey.setPartNumber(partNumber);
pkey.setRevision(revision);

Part part = em.find(Part.class, pkey);

VendorPart vendorPart = new VendorPart(description, price, part);
em.persist(vendorPart);

Vendor vendor = em.find(Vendor.class, vendorId);
vendor.addVendorPart(vendorPart);
vendorPart.setVendor(vendor);

Using Queries

The RequestBean.adjustOrderDiscount business method updates the discount applied to all orders. This method uses the findAllOrders named query, defined in CustomerOrder:

@NamedQuery(
    name="findAllOrders",
    query="SELECT co FROM CustomerOrder co " +
          "ORDER BY co.orderId"
)

The EntityManager.createNamedQuery method is used to run the query. Because the query returns a List of all the orders, the Query.getResultList method is used:

List orders = em.createNamedQuery(
        "findAllOrders")
        .getResultList();

The RequestBean.getTotalPricePerVendor business method returns the total price of all the parts for a particular vendor. This method uses a named parameter, id, defined in the named query findTotalVendorPartPricePerVendor defined in VendorPart:

@NamedQuery(
    name="findTotalVendorPartPricePerVendor",
    query="SELECT SUM(vp.price) " +
    "FROM VendorPart vp " +
    "WHERE vp.vendor.vendorId = :id"
)

When running the query, the Query.setParameter method is used to set the named parameter id to the value of vendorId, the parameter to RequestBean.getTotalPricePerVendor:

return (Double) em.createNamedQuery(
    "findTotalVendorPartPricePerVendor")
    .setParameter("id", vendorId)
    .getSingleResult();

The Query.getSingleResult method is used for this query because the query returns a single value.

Removing Entities

The RequestBean.removeOrder business method deletes a given order from the database. This method uses the EntityManager.remove method to delete the entity from the database:

CustomerOrder order = em.find(CustomerOrder.class, orderId);
em.remove(order);

Running the order Example

You can use either NetBeans IDE or Maven to build, package, deploy, and run the order application. First, you will create the database tables in Apache Derby.

To Run the order Example Using NetBeans IDE

Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).
If the database server is not already running, start it by following the instructions in Starting and Stopping Apache Derby.
From the File menu, choose Open Project.
In the Open Project dialog box, navigate to:
```
jakartaee-examples/tutorial/persistence
```
Select the order folder.
Click Open Project.
In the Projects tab, right-click the order project and select Run.

NetBeans IDE opens a web browser to the following URL:
```
http://localhost:8080/order/
```

To Run the order Example Using Maven

Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).
If the database server is not already running, start it by following the instructions in Starting and Stopping Apache Derby.

In a terminal window, go to:

jakartaee-examples/tutorial/persistence/order/

Enter the following command:
```
mvn install
```
This compiles the source files and packages the application into a WAR file located at jakartaee-examples/tutorial/persistence/order/target/order.war. Then the WAR file is deployed to your GlassFish Server instance.
To create and update the order data, open a web browser to the following URL:
```
http://localhost:8080/order/
```

The roster Application

The roster application maintains the team rosters for players in recreational sports leagues. The application has four components: Jakarta Persistence entities (Player, Team, and League), a stateful session bean (RequestBean), an application client (RosterClient), and three helper classes (PlayerDetails, TeamDetails, and LeagueDetails).

Functionally, roster is similar to the order application, with three new features that order does not have: many-to-many relationships, entity inheritance, and automatic table creation at deployment time.

The database schema in Apache Derby for the roster application is shown in Figure 2, “Database Schema for the roster Application”.

Diagram showing the database schema for the roster application

Figure 2. Database Schema for the roster Application

In this diagram, for simplicity, the PERSISTENCE_ROSTER_ prefix is omitted from the table names.

Relationships in the roster Application

A recreational sports system has the following relationships.

A player can be on many teams.
A team can have many players.
A team is in exactly one league.
A league has many teams.

In roster this system is reflected by the following relationships between the Player, Team, and League entities.

There is a many-to-many relationship between Player and Team.
There is a many-to-one relationship between Team and League.

The Many-To-Many Relationship in roster

The many-to-many relationship between Player and Team is specified by using the @ManyToMany annotation. In Team.java, the @ManyToMany annotation decorates the getPlayers method:

@ManyToMany
@JoinTable(
    name="PERSISTENCE_ROSTER_TEAM_PLAYER",
    joinColumns=
        @JoinColumn(name="TEAM_ID", referencedColumnName="ID"),
    inverseJoinColumns=
        @JoinColumn(name="PLAYER_ID", referencedColumnName="ID")
)
public Collection<Player> getPlayers() {
    return players;
}

The @JoinTable annotation is used to specify a database table that will associate player IDs with team IDs. The entity that specifies the @JoinTable is the owner of the relationship, so the Team entity is the owner of the relationship with the Player entity. Because roster uses automatic table creation at deployment time, the container will create a join table named PERSISTENCE_ROSTER_TEAM_PLAYER.

Player is the inverse, or nonowning, side of the relationship with Team. As one-to-one and many-to-one relationships, the nonowning side is marked by the mappedBy element in the relationship annotation. Because the relationship between Player and Team is bidirectional, the choice of which entity is the owner of the relationship is arbitrary.

In Player.java, the @ManyToMany annotation decorates the getTeams method:

@ManyToMany(mappedBy="players")
public Collection<Team> getTeams() {
    return teams;
}

Entity Inheritance in the roster Application

The roster application shows how to use entity inheritance, as described in Entity Inheritance.

The League entity in roster is an abstract entity with two concrete subclasses: SummerLeague and WinterLeague. Because League is an abstract class, it cannot be instantiated:

@Entity
@Table(name = "PERSISTENCE_ROSTER_LEAGUE")
public abstract class League implements Serializable { ... }

Instead, when creating a league, clients use SummerLeague or WinterLeague. SummerLeague and WinterLeague inherit the persistent properties defined in League and add only a constructor that verifies that the sport parameter matches the type of sport allowed in that seasonal league. For example, here is the SummerLeague entity:

...
@Entity
public class SummerLeague extends League implements Serializable {

    /** Creates a new instance of SummerLeague */
    public SummerLeague() {
    }

    public SummerLeague(String id, String name, String sport)
            throws IncorrectSportException {
        this.id = id;
        this.name = name;
        if (sport.equalsIgnoreCase("swimming") ||
                sport.equalsIgnoreCase("soccer") ||
                sport.equalsIgnoreCase("basketball") ||
                sport.equalsIgnoreCase("baseball")) {
            this.sport = sport;
        } else {
            throw new IncorrectSportException("Sport is not a summer sport.");
        }
    }
}

The roster application uses the default mapping strategy of InheritanceType.SINGLE_TABLE, so the @Inheritance annotation is not required. If you want to use a different mapping strategy, decorate League with @Inheritance and specify the mapping strategy in the strategy element:

@Entity
@Inheritance(strategy=JOINED)
@Table(name="PERSISTENCE_ROSTER_LEAGUE")
public abstract class League implements Serializable { ... }

The roster application uses the default discriminator column name, so the @DiscriminatorColumn annotation is not required. Because you are using automatic table generation in roster, the Persistence provider will create a discriminator column called DTYPE in the PERSISTENCE_ROSTER_LEAGUE table, which will store the name of the inherited entity used to create the league. If you want to use a different name for the discriminator column, decorate League with @DiscriminatorColumn and set the name element:

@Entity
@DiscriminatorColumn(name="DISCRIMINATOR")
@Table(name="PERSISTENCE_ROSTER_LEAGUE")
public abstract class League implements Serializable { ... }

Criteria Queries in the roster Application

The roster application uses Criteria API queries, as opposed to the JPQL queries used in order. Criteria queries are Java programming language, typesafe queries defined in the business tier of roster, in the RequestBean stateful session bean.

Metamodel Classes in the roster Application

Metamodel classes model an entity’s attributes and are used by Criteria queries to navigate to an entity’s attributes. Each entity class in roster has a corresponding metamodel class, generated at compile time, with the same package name as the entity and appended with an underscore character (_). For example, the roster.entity.Player entity has a corresponding metamodel class, roster.entity.Player_.

Each persistent field or property in the entity class has a corresponding attribute in the entity’s metamodel class. For the Player entity, the corresponding metamodel class is as follows:

@StaticMetamodel(Player.class)
public class Player_ {
    public static volatile SingularAttribute<Player, String> id;
    public static volatile SingularAttribute<Player, String> name;
    public static volatile SingularAttribute<Player, String> position;
    public static volatile SingularAttribute<Player, Double> salary;
    public static volatile CollectionAttribute<Player, Team> teams;
}

Obtaining a CriteriaBuilder Instance in RequestBean

The CriteriaBuilder interface defines methods to create criteria query objects and create expressions for modifying those query objects. RequestBean creates an instance of CriteriaBuilder by using a @PostConstruct method, init:

@PersistenceContext
private EntityManager em;
private CriteriaBuilder cb;

@PostConstruct
private void init() {
    cb = em.getCriteriaBuilder();
}

The EntityManager instance is injected at runtime, and then that EntityManager object is used to create the CriteriaBuilder instance by calling getCriteriaBuilder. The CriteriaBuilder instance is created in a @PostConstruct method to ensure that the EntityManager instance has been injected by the enterprise bean container.

Creating Criteria Queries in RequestBean’s Business Methods

Many of the business methods in RequestBean define Criteria queries. One business method, getPlayersByPosition, returns a list of players who play a particular position on a team:

public List<PlayerDetails> getPlayersByPosition(String position) {
    logger.info("getPlayersByPosition");
    List<Player> players = null;

    try {
        CriteriaQuery<Player> cq = cb.createQuery(Player.class);
        if (cq != null) {
            Root<Player> player = cq.from(Player.class);

            // set the where clause
            cq.where(cb.equal(player.get(Player_.position), position));
            cq.select(player);
            TypedQuery<Player> q = em.createQuery(cq);
            players = q.getResultList();
        }
        return copyPlayersToDetails(players);
    } catch (Exception ex) {
        throw new EJBException(ex);
    }
}

A query object is created by calling the CriteriaBuilder object’s createQuery method, with the type set to Player because the query will return a list of players.

The query root, the base entity from which the query will navigate to find the entity’s attributes and related entities, is created by calling the from method of the query object. This sets the FROM clause of the query.

The WHERE clause, set by calling the where method on the query object, restricts the results of the query according to the conditions of an expression. The CriteriaBuilder.equal method compares the two expressions. In getPlayersByPosition, the position attribute of the Player_ metamodel class, accessed by calling the get method of the query root, is compared to the position parameter passed to getPlayersByPosition.

The SELECT clause of the query is set by calling the select method of the query object. The query will return Player entities, so the query root object is passed as a parameter to select.

The query object is prepared for execution by calling EntityManager.createQuery, which returns a TypedQuery<T> object with the type of the query, in this case Player. This typed query object is used to execute the query, which occurs when the getResultList method is called, and a List<Player> collection is returned.

Automatic Table Generation in the roster Application

At deployment time, GlassFish Server will automatically drop and create the database tables used by roster. This is done by setting the jakarta.persistence.schema-generation.database.action property to drop-and-create in persistence.xml:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="3.0"
    xmlns="https://jakarta.ee/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="https://jakarta.ee/xml/ns/persistence
        https://jakarta.ee/xml/ns/persistence/persistence_3_0.xsd">
  <persistence-unit name="em" transaction-type="JTA">
    <jta-data-source>java:comp/DefaultDataSource</jta-data-source>
    <properties>
      <property name="jakarta.persistence.schema-generation.database.action"
                value="drop-and-create"/>
    </properties>
  </persistence-unit>
</persistence>

Running the roster Example

You can use either NetBeans IDE or Maven to build, package, deploy, and run the roster application.

To Run the roster Example Using NetBeans IDE

Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).
If the database server is not already running, start it by following the instructions in Starting and Stopping Apache Derby.
From the File menu, choose Open Project.
In the Open Project dialog box, navigate to:
```
jakartaee-examples/tutorial/persistence
```
Select the roster folder.
Select the Open Required Projects check box.
Click Open Project.

In the Projects tab, right-click the roster project and select Build.

This will compile, package, and deploy the EAR to GlassFish Server.

You will see the following partial output from the application client in the Output tab:

List all players in team T2:
P6 Ian Carlyle goalkeeper 555.0
P7 Rebecca Struthers midfielder 777.0
P8 Anne Anderson forward 65.0
P9 Jan Wesley defender 100.0
P10 Terry Smithson midfielder 100.0

List all teams in league L1:
T1 Honey Bees Visalia
T2 Gophers Manteca
T5 Crows Orland

List all defenders:
P2 Alice Smith defender 505.0
P5 Barney Bold defender 100.0
P9 Jan Wesley defender 100.0
P22 Janice Walker defender 857.0
P25 Frank Fletcher defender 399.0

To Run the roster Example Using Maven

Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).
If the database server is not already running, start it by following the instructions in Starting and Stopping Apache Derby.

In a terminal window, go to:

jakartaee-examples/tutorial/persistence/roster/roster-ear/

Enter the following command:

mvn install

This compiles the source files and packages the application into an EAR file located at jakartaee-examples/tutorial/persistence/roster/target/roster.ear. The EAR file is then deployed to GlassFish Server. GlassFish Server will then drop and create the database tables during deployment, as specified in persistence.xml.

After successfully deploying the EAR, the client stubs are retrieved and the application client is run using the appclient application included with GlassFish Server.

You will see the output, which begins as follows:

[echo] running application client container.
[exec] List all players in team T2:
[exec] P6 Ian Carlyle goalkeeper 555.0
[exec] P7 Rebecca Struthers midfielder 777.0
[exec] P8 Anne Anderson forward 65.0
[exec] P9 Jan Wesley defender 100.0
[exec] P10 Terry Smithson midfielder 100.0

[exec] List all teams in league L1:
[exec] T1 Honey Bees Visalia
[exec] T2 Gophers Manteca
[exec] T5 Crows Orland

[exec] List all defenders:
[exec] P2 Alice Smith defender 505.0
[exec] P5 Barney Bold defender 100.0
[exec] P9 Jan Wesley defender 100.0
[exec] P22 Janice Walker defender 857.0
[exec] P25 Frank Fletcher defender 399.0

The address-book Application

The address-book example application is a simple web application that stores contact data. It uses a single entity class, Contact, that uses Jakarta Bean Validation to validate the data stored in the persistent attributes of the entity, as described in Validating Persistent Fields and Properties.

Bean Validation Constraints in address-book

The Contact entity uses the @NotNull, @Pattern, and @Past constraints on the persistent attributes.

The @NotNull constraint marks the attribute as a required field. The attribute must be set to a non-null value before the entity can be persisted or modified. Bean Validation will throw a validation error if the attribute is null when the entity is persisted or modified.

The @Pattern constraint defines a regular expression that the value of the attribute must match before the entity can be persisted or modified. This constraint has two different uses in address-book.

The regular expression declared in the @Pattern annotation on the email field matches email addresses of the form name@domain name.top level domain, allowing only valid characters for email addresses. For example, username@example.com will pass validation, as will firstname.lastname@mail.example.com. However, firstname,lastname@example.com, which contains an illegal comma character in the local name, will fail validation.
The mobilePhone and homePhone fields are annotated with a @Pattern constraint that defines a regular expression to match phone numbers of the form (xxx) xxx-xxxx.

The @Past constraint is applied to the birthday field, which must be a java.util.Date in the past.

Here are the relevant parts of the Contact entity class:

@Entity
public class Contact implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    @NotNull
    protected String firstName;
    @NotNull
    protected String lastName;
    @Pattern(regexp = "[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\."
            + "[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@"
            + "(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9]"
            + "(?:[a-z0-9-]*[a-z0-9])?",
            message = "{invalid.email}")
    protected String email;
    @Pattern(regexp = "^\\(?(\\d{3})\\)?[- ]?(\\d{3})[- ]?(\\d{4})$",
            message = "{invalid.phonenumber}")
    protected String mobilePhone;
    @Pattern(regexp = "^\\(?(\\d{3})\\)?[- ]?(\\d{3})[- ]?(\\d{4})$",
            message = "{invalid.phonenumber}")
    protected String homePhone;
    @Temporal(jakarta.persistence.TemporalType.DATE)
    @Past
    protected Date birthday;
    ...
}

Specifying Error Messages for Constraints in address-book

Some of the constraints in the Contact entity specify an optional message:

@Pattern(regexp = "^\\(?(\\d{3})\\)?[- ]?(\\d{3})[- ]?(\\d{4})$",
        message = "{invalid.phonenumber}")
protected String homePhone;

The optional message element in the @Pattern constraint overrides the default validation message. The message can be specified directly:

@Pattern(regexp = "^\\(?(\\d{3})\\)?[- ]?(\\d{3})[- ]?(\\d{4})$",
        message = "Invalid phone number!")
protected String homePhone;

The constraints in Contact, however, are strings in the resource bundle ValidationMessages.properties, under jakartaee-examples/tutorial/persistence/address-book/src/main/java. This allows the validation messages to be located in one single properties file and the messages to be easily localized. Overridden Bean Validation messages must be placed in a resource bundle properties file named ValidationMessages.properties in the default package, with localized resource bundles taking the form ValidationMessages_locale-prefix.properties. For example, ValidationMessages_es.properties is the resource bundle used in Spanish-speaking locales.

Validating Contact Input from a Jakarta Faces Application

The address-book application uses a Jakarta Faces web front end to allow users to enter contacts. While Jakarta Faces has a form input validation mechanism using tags in Facelets XHTML files, address-book doesn’t use these validation tags. Bean Validation constraints in Jakarta Faces managed beans, in this case in the Contact entity, automatically trigger validation when the forms are submitted.

The following code snippet from the Create.xhtml Facelets file shows some of the input form for creating new Contact instances:

<h:form>
    <table columns="3" role="presentation">
        <tr>
            <td><h:outputLabel value="#{bundle.CreateContactLabel_firstName}"
                               for="firstName" /></td>
            <td><h:inputText id="firstName"
                             value="#{contactController.selected.firstName}"
                             title="#{bundle.CreateContactTitle_firstName}"/>
            </td>
            <td><h:message for="firstName" /></td>
        </tr>
        <tr>
            <td><h:outputLabel value="#{bundle.CreateContactLabel_lastName}"
                               for="lastName" /></td>
            <td><h:inputText id="lastName"
                             value="#{contactController.selected.lastName}"
                             title="#{bundle.CreateContactTitle_lastName}" />
            </td>
            <td><h:message for="lastName" /></td>
        </tr>
        ...
    </table>
</h:form>

The <h:inputText> tags firstName and lastName are bound to the attributes in the Contact entity instance selected in the ContactController stateless session bean. Each <h:inputText> tag has an associated <h:message> tag that will display validation error messages. The form doesn’t require any Jakarta Faces validation tags, however.

Running the address-book Example

You can use either NetBeans IDE or Maven to build, package, deploy, and run the address-book application.

To Run the address-book Example Using NetBeans IDE

Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).
If the database server is not already running, start it by following the instructions in Starting and Stopping Apache Derby.
From the File menu, choose Open Project.
In the Open Project dialog box, navigate to:
```
jakartaee-examples/tutorial/persistence
```
Select the address-book folder.
Click Open Project.
In the Projects tab, right-click the address-book project and select Run.

After the application has been deployed, a web browser window appears at the following URL:
```
http://localhost:8080/address-book/
```
Click Show All Contact Items, then Create New Contact. Enter values in the fields; then click Save.

If any of the values entered violate the constraints in Contact, an error message will appear in red beside the field with the incorrect values.

To Run the address-book Example Using Maven

Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).
If the database server is not already running, start it by following the instructions in Starting and Stopping Apache Derby.

In a terminal window, go to:

jakartaee-examples/tutorial/persistence/address-book/

Enter the following command:
```
mvn install
```
This will compile and assemble the address-book application into a WAR. The WAR file is then deployed to GlassFish Server.
Open a web browser window and enter the following URL:
```
http://localhost:8080/address-book/
```
Click Show All Contact Items, then Create New Contact. Enter values in the fields; then click Save.

If any of the values entered violate the constraints in Contact, an error message will appear in red beside the field with the incorrect values.