java - 如何在实体类中传递自动增量值以保存到数据库中

Question

我正在练习 JSF + EJB + JPA + DERBY 应用程序。我面临的问题是我无法使用 EJB 和 JPA 将自动增量值发送到数据库。代码和问题解释如下:

其中一个数据库表包含自动增量主键。表只有 2 列，例如“id”和“name”。 “id”是自增主键。

表的实体类代码为:

package entities;

import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.validation.constraints.Size;
import javax.xml.bind.annotation.XmlRootElement;

@Entity
@Table(name = "EMPLOYEES")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Employees.findAll", query = "SELECT e FROM Employees e"),
    @NamedQuery(name = "Employees.findById", query = "SELECT e FROM Employees e WHERE e.id = :id"),
    @NamedQuery(name = "Employees.findByName", query = "SELECT e FROM Employees e WHERE e.name = :name")})
public class Employees implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = true)
    @Column(name = "ID")
    private Integer id;
    @Size(max = 255)
    @Column(name = "NAME")
    private String name;

    public Employees() {
    }

    public Employees(Integer id) {
        this.id = id;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Employees)) {
            return false;
        }
        Employees other = (Employees) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "entities.Employees[ id=" + id + " ]";
    }
}

实体类的 EJB 接口(interface)和类是:

package ejb;

import entities.Employees;
import java.util.List;
import javax.ejb.Local;


@Local
public interface EmployeesFacadeLocal {

    void create(Employees employees);

    void edit(Employees employees);

    void remove(Employees employees);

    Employees find(Object id);

    List<Employees> findAll();

    List<Employees> findRange(int[] range);

    int count();

}

package ejb;

import entities.Employees;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Stateless
public class EmployeesFacade extends AbstractFacade<Employees> implements EmployeesFacadeLocal {
    @PersistenceContext(unitName = "UsingEntitiesPU")
    private EntityManager em;

    @Override
    protected EntityManager getEntityManager() {
        return em;
    }

    public EmployeesFacade() {
        super(Employees.class);
    }

    @Override
    public void create(Employees emp) {
        em.persist(emp);
    }

}

JSF 托管 Bean 代码:

package web;

import ejb.EmployeesFacadeLocal;
import entities.Employees;
import java.io.Serializable;
import javax.ejb.EJB;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;


@ManagedBean
@SessionScoped
public class index implements Serializable {

    @EJB
    EmployeesFacadeLocal employee;
    /**
     * Creates a new instance of index
     */

    private String name = "";

    public index() {
    }

    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void saveEmployee() {
        Employees emp = new Employees();
        emp.setId(Integer.SIZE);
        emp.setName(this.name);
        employee.create(emp);
    }

}

JSF View 代码:

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://xmlns.jcp.org/jsf/html">
    <h:head>
        <title>Facelet Title</title>
    </h:head>
    <h:body>
        <h:form>
            <table>
                <tr>
                    <td>Name:</td>
                    <td><h:inputText value="#{index.name}" /></td>
                </tr>
                <tr>
                    <td></td>
                    <td><h:commandButton value="Save" action="#{index.saveEmployee()}" /></td>
                </tr>
            </table>
        </h:form>
    </h:body>
</html>

当我一起运行此代码时，我收到以下异常:

javax.faces.el.EvaluationException: javax.ejb.EJBException: Transaction aborted
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
    at javax.faces.component.UICommand.broadcast(UICommand.java:315)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:415)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
    at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
    at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
    at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
    at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
    at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
    at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
    at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561)
    at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
    at java.lang.Thread.run(Thread.java:745)
Caused by: javax.ejb.EJBException: Transaction aborted
    at com.sun.ejb.containers.EJBContainerTransactionManager.completeNewTx(EJBContainerTransactionManager.java:725)
    at com.sun.ejb.containers.EJBContainerTransactionManager.postInvokeTx(EJBContainerTransactionManager.java:503)
    at com.sun.ejb.containers.BaseContainer.postInvokeTx(BaseContainer.java:4566)
    at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:2074)
    at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:2044)
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:220)
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandlerDelegate.invoke(EJBLocalObjectInvocationHandlerDelegate.java:88)
    at com.sun.proxy.$Proxy310.create(Unknown Source)
    at web.index.saveEmployee(index.java:46)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at javax.el.ELUtil.invokeMethod(ELUtil.java:332)
    at javax.el.BeanELResolver.invoke(BeanELResolver.java:537)
    at javax.el.CompositeELResolver.invoke(CompositeELResolver.java:256)
    at com.sun.el.parser.AstValue.invoke(AstValue.java:283)
    at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:304)
    at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:40)
    at org.jboss.weld.el.WeldMethodExpression.invoke(WeldMethodExpression.java:50)
    at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
    ... 36 more
Caused by: javax.transaction.RollbackException: Transaction marked for rollback.
    at com.sun.enterprise.transaction.JavaEETransactionImpl.commit(JavaEETransactionImpl.java:490)
    at com.sun.enterprise.transaction.JavaEETransactionManagerSimplified.commit(JavaEETransactionManagerSimplified.java:854)
    at com.sun.ejb.containers.EJBContainerTransactionManager.completeNewTx(EJBContainerTransactionManager.java:719)
    ... 57 more
Caused by: javax.persistence.PersistenceException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: java.sql.SQLSyntaxErrorException: Table/View 'EMPLOYEES' does not exist.
Error Code: 20000
Call: INSERT INTO EMPLOYEES (NAME) VALUES (?)
    bind => [1 parameter bound]
Query: InsertObjectQuery(entities.Employees[ id=32 ])
    at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl$1.handleException(EntityManagerSetupImpl.java:696)
    at org.eclipse.persistence.transaction.AbstractSynchronizationListener.handleException(AbstractSynchronizationListener.java:275)
    at org.eclipse.persistence.transaction.AbstractSynchronizationListener.beforeCompletion(AbstractSynchronizationListener.java:170)
    at org.eclipse.persistence.transaction.JTASynchronizationListener.beforeCompletion(JTASynchronizationListener.java:68)
    at com.sun.enterprise.transaction.JavaEETransactionImpl.commit(JavaEETransactionImpl.java:452)
    ... 59 more
Caused by: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: java.sql.SQLSyntaxErrorException: Table/View 'EMPLOYEES' does not exist.
Error Code: 20000
Call: INSERT INTO EMPLOYEES (NAME) VALUES (?)
    bind => [1 parameter bound]
Query: InsertObjectQuery(entities.Employees[ id=32 ])
    at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:340)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:682)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeCall(DatabaseAccessor.java:558)
    at org.eclipse.persistence.internal.sessions.AbstractSession.basicExecuteCall(AbstractSession.java:2002)
    at org.eclipse.persistence.sessions.server.ClientSession.executeCall(ClientSession.java:298)
    at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:242)
    at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:228)
    at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.insertObject(DatasourceCallQueryMechanism.java:377)
    at org.eclipse.persistence.internal.queries.StatementQueryMechanism.insertObject(StatementQueryMechanism.java:165)
    at org.eclipse.persistence.internal.queries.StatementQueryMechanism.insertObject(StatementQueryMechanism.java:180)
    at org.eclipse.persistence.internal.queries.DatabaseQueryMechanism.insertObjectForWrite(DatabaseQueryMechanism.java:489)
    at org.eclipse.persistence.queries.InsertObjectQuery.executeCommit(InsertObjectQuery.java:80)
    at org.eclipse.persistence.queries.InsertObjectQuery.executeCommitWithChangeSet(InsertObjectQuery.java:90)
    at org.eclipse.persistence.internal.queries.DatabaseQueryMechanism.executeWriteWithChangeSet(DatabaseQueryMechanism.java:301)
    at org.eclipse.persistence.queries.WriteObjectQuery.executeDatabaseQuery(WriteObjectQuery.java:58)
    at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:899)
    at org.eclipse.persistence.queries.DatabaseQuery.executeInUnitOfWork(DatabaseQuery.java:798)
    at org.eclipse.persistence.queries.ObjectLevelModifyQuery.executeInUnitOfWorkObjectLevelModifyQuery(ObjectLevelModifyQuery.java:108)
    at org.eclipse.persistence.queries.ObjectLevelModifyQuery.executeInUnitOfWork(ObjectLevelModifyQuery.java:85)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery(UnitOfWorkImpl.java:2896)
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1804)
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1786)
    at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1737)
    at org.eclipse.persistence.internal.sessions.CommitManager.commitNewObjectsForClassWithChangeSet(CommitManager.java:226)
    at org.eclipse.persistence.internal.sessions.CommitManager.commitAllObjectsWithChangeSet(CommitManager.java:125)
    at org.eclipse.persistence.internal.sessions.AbstractSession.writeAllObjectsWithChangeSet(AbstractSession.java:4207)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commitToDatabase(UnitOfWorkImpl.java:1441)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commitToDatabaseWithChangeSet(UnitOfWorkImpl.java:1531)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.issueSQLbeforeCompletion(UnitOfWorkImpl.java:3168)
    at org.eclipse.persistence.internal.sessions.RepeatableWriteUnitOfWork.issueSQLbeforeCompletion(RepeatableWriteUnitOfWork.java:352)
    at org.eclipse.persistence.transaction.AbstractSynchronizationListener.beforeCompletion(AbstractSynchronizationListener.java:158)
    ... 61 more
Caused by: java.sql.SQLSyntaxErrorException: Table/View 'EMPLOYEES' does not exist.
    at org.apache.derby.client.am.SQLExceptionFactory40.getSQLException(Unknown Source)
    at org.apache.derby.client.am.SqlException.getSQLException(Unknown Source)
    at org.apache.derby.client.am.Connection.prepareStatement(Unknown Source)
    at com.sun.gjc.spi.base.ConnectionHolder.prepareStatement(ConnectionHolder.java:586)
    at com.sun.gjc.spi.jdbc40.ConnectionWrapper40.prepareCachedStatement(ConnectionWrapper40.java:255)
    at com.sun.gjc.spi.jdbc40.ConnectionWrapper40.prepareCachedStatement(ConnectionWrapper40.java:52)
    at com.sun.gjc.spi.ManagedConnectionImpl.prepareCachedStatement(ManagedConnectionImpl.java:992)
    at com.sun.gjc.spi.jdbc40.ConnectionWrapper40.prepareStatement(ConnectionWrapper40.java:173)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.prepareStatement(DatabaseAccessor.java:1556)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.prepareStatement(DatabaseAccessor.java:1505)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseCall.prepareStatement(DatabaseCall.java:778)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:619)
    ... 90 more
Caused by: org.apache.derby.client.am.SqlException: Table/View 'EMPLOYEES' does not exist.
    at org.apache.derby.client.am.Statement.completeSqlca(Unknown Source)
    at org.apache.derby.client.net.NetStatementReply.parsePrepareError(Unknown Source)
    at org.apache.derby.client.net.NetStatementReply.parsePRPSQLSTTreply(Unknown Source)
    at org.apache.derby.client.net.NetStatementReply.readPrepareDescribeOutput(Unknown Source)
    at org.apache.derby.client.net.StatementReply.readPrepareDescribeOutput(Unknown Source)
    at org.apache.derby.client.net.NetStatement.readPrepareDescribeOutput_(Unknown Source)
    at org.apache.derby.client.am.Statement.readPrepareDescribeOutput(Unknown Source)
    at org.apache.derby.client.am.PreparedStatement.readPrepareDescribeInputOutput(Unknown Source)
    at org.apache.derby.client.am.PreparedStatement.flowPrepareDescribeInputOutput(Unknown Source)
    at org.apache.derby.client.am.PreparedStatement.prepare(Unknown Source)
    at org.apache.derby.client.am.Connection.prepareStatementX(Unknown Source)
    ... 100 more

Persistence.xml 文件:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
  <persistence-unit name="UsingEntitiesPU" transaction-type="JTA">
    <jta-data-source>JNDIEmployees</jta-data-source>
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <properties/>
  </persistence-unit>
</persistence>

glassfish-resources.xml 文件:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE resources PUBLIC "-//GlassFish.org//DTD GlassFish Application Server 3.1 Resource Definitions//EN" "http://glassfish.org/dtds/glassfish-resources_1_5.dtd">
<resources>
    <jdbc-connection-pool allow-non-component-callers="false" associate-with-thread="false" connection-creation-retry-attempts="0" connection-creation-retry-interval-in-seconds="10" connection-leak-reclaim="false" connection-leak-timeout-in-seconds="0" connection-validation-method="auto-commit" datasource-classname="org.apache.derby.jdbc.ClientDataSource" fail-all-connections="false" idle-timeout-in-seconds="300" is-connection-validation-required="false" is-isolation-level-guaranteed="true" lazy-connection-association="false" lazy-connection-enlistment="false" match-connections="false" max-connection-usage-count="0" max-pool-size="32" max-wait-time-in-millis="60000" name="derby_net_ShoppingCart_appPool" non-transactional-connections="false" pool-resize-quantity="2" res-type="javax.sql.DataSource" statement-timeout-in-seconds="-1" steady-pool-size="8" validate-atmost-once-period-in-seconds="0" wrap-jdbc-objects="false">
        <property name="serverName" value="localhost"/>
        <property name="portNumber" value="1527"/>
        <property name="databaseName" value="ShoppingCart"/>
        <property name="User" value="app"/>
        <property name="Password" value="app"/>
        <property name="URL" value="jdbc:derby://localhost:1527/ShoppingCart"/>
        <property name="driverClass" value="org.apache.derby.jdbc.ClientDriver"/>
    </jdbc-connection-pool>
    <jdbc-resource enabled="true" jndi-name="JNDIEmployees" object-type="user" pool-name="derby_net_ShoppingCart_appPool"/>
</resources>

看起来实体类对运行时提供的自动增量值不满意。

在实体类中我已经在使用

@GeneratedValue(strategy = GenerationType.IDENTITY)

为了让它快乐，但现在，我不确定什么是异常(exception)。

请帮助我理解 EJB 和 JPA 如何处理自动增量列。

Answer 1

这是连接池的问题。连接池没有适当的数据库名称、用户名、密码和连接值。

通过使用 GlassFish 的管理控制台，我为连接池提供了适当的数据库值，现在一切正常:-)