JAVA JPA - 示例用法

2022-11-14 21:01:57

JPA(Java Persistence API)是JSR(Java Specification Requests)的一部分，定义了一系列对象持久化的标准，目前实现这一规范的产品有Hibernate、TopLink等。

下面的示例程序是在jboss quickStart的基础上修改而来的

1、实体Bean：Member类

 package org.jboss.as.quickstart.hibernate4.model;

 import java.io.Serializable;

 import javax.persistence.Column;

 import javax.persistence.Entity;

 import javax.persistence.GeneratedValue;

 import javax.persistence.GenerationType;

 import javax.persistence.Id;

 import javax.persistence.SequenceGenerator;

 import javax.persistence.Table;

 import javax.validation.constraints.Digits;

 import javax.validation.constraints.NotNull;

 import javax.validation.constraints.Pattern;

 import javax.validation.constraints.Size;

 import javax.xml.bind.annotation.XmlRootElement;

 import org.hibernate.validator.constraints.Email;

 import org.hibernate.validator.constraints.NotEmpty;

 @Entity

 @XmlRootElement

 @Table(name = "MemberHibernate4Demo")

 public class Member implements Serializable {

     private static final long serialVersionUID = 3862416351900991824L;

     @Id

     @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "MEMBER_ID_GENERATOR")

     @SequenceGenerator(name = "MEMBER_ID_GENERATOR", sequenceName = "SEQ_MEMBER", allocationSize = 1)

     private Long id;

     @NotNull

     @Size(min = 1, max = 25)

     @Pattern(regexp = "[A-Za-z ]*", message = "must contain only letters and spaces")

     private String name;

     @NotNull

     @NotEmpty

     @Email

     private String email;

     @NotNull

     @Size(min = 9, max = 12)

     @Digits(fraction = 0, integer = 12)

     @Column(name = "phone_number")

     private String phoneNumber;

     private String address;

     public Long getId() {

         return id;

     }

     public void setId(Long id) {

         this.id = id;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public String getEmail() {

         return email;

     }

     public void setEmail(String email) {

         this.email = email;

     }

     public String getPhoneNumber() {

         return phoneNumber;

     }

     public void setPhoneNumber(String phoneNumber) {

         this.phoneNumber = phoneNumber;

     }

     public String getAddress() {

         return address;

     }

     public void setAddress(String address) {

         this.address = address;

     }

     public String toString() {

         return "id:" + id + ",name:" + name + ",email:" + email

                 + ",phoneNumber:" + phoneNumber + ",address:" + address;

     }

 }

Member

注意：私有成员id上的注解@SequenceGenerator、@GeneratedValue演示Oracle中序列（Sequence）的用法。

2、服务接口 MemberService

 package org.jboss.as.quickstart.hibernate4.service;

 import java.util.List;

 import org.jboss.as.quickstart.hibernate4.model.Member;

 public interface MemberService {

     void addMember(Member member) throws Exception;

     void updateMember(Member member) throws Exception;

     void deleteMember(long id) throws Exception;

     Member findMember(long id) throws Exception;

     List<Member> getMembers() throws Exception;

 }

MemberService

3、服务实现 MemberServiceImpl

 package org.jboss.as.quickstart.hibernate4.service;

 import java.util.logging.Logger;

 import java.util.List;

 import javax.ejb.Stateless;

 import javax.enterprise.event.Event;

 import javax.inject.Inject;

 import javax.persistence.EntityManager;

 import javax.persistence.PersistenceContext;

 import org.jboss.as.quickstart.hibernate4.model.Member;

 @Stateless

 public class MemberServiceImpl implements MemberService {

     @PersistenceContext

     private EntityManager em;

     @Inject

     private Logger log;

     @Inject

     private Event<Member> memberEventSrc;

     @Override

     public void addMember(Member member) throws Exception {

         log.info("addMember => " + member.toString());

         member.setId(null);

         em.persist(member);

         memberEventSrc.fire(member);

     }

     @Override

     public void updateMember(Member member) throws Exception {

         log.info("updateMember => " + member.getName());

         if (member.getId() > 0) {

             Member updateObj = findMember(member.getId());

             updateObj.setAddress(member.getAddress());

             updateObj.setEmail(member.getEmail());

             updateObj.setName(member.getName());

             updateObj.setPhoneNumber(member.getPhoneNumber());

             em.merge(updateObj);

             memberEventSrc.fire(updateObj);

         }

     }

     @Override

     public void deleteMember(long id) throws Exception {

         log.info("deleteMember => " + id);

         Member member = findMember(id);

         em.remove(member);

         memberEventSrc.fire(member);

     }

     @Override

     public List<Member> getMembers() throws Exception {

         @SuppressWarnings("unchecked")

         List<Member> members = em.createQuery("from Member").getResultList();

         return members;

     }

     @Override

     public Member findMember(long id) throws Exception {

         log.info("findMember => " + id);

         return em.find(Member.class, id);

     }

 }

MemberService

注意：此外大量使用了CDI来实现对象的依赖注入，@PersistenceContext 用于在EJB容器中自动注入"实体管理器"（所以类上要使用@Stateless表示，这是一个无状态的EJB），上面这段代码演示了数据的基础CRUD(Create、Retrieve、Update、Delete)操作，另外为了配合CDI的@Inject注入，还需要一些@Produces的辅助工具类。(对CDI不熟悉的，可以先看看这里http://www.cnblogs.com/yjmyzz/p/j2ee-cdi-inject.html)

4、辅助类 Resouces

 package org.jboss.as.quickstart.hibernate4.util;

 import java.util.Map;

 import java.util.logging.Logger;

 import javax.enterprise.context.RequestScoped;

 import javax.enterprise.inject.Produces;

 import javax.enterprise.inject.spi.InjectionPoint;

 import javax.faces.context.FacesContext;

 public class Resources {

     @Produces

     public Logger produceLog(InjectionPoint injectionPoint) {

         return Logger.getLogger(injectionPoint.getMember().getDeclaringClass()

                 .getName());

     }

     @Produces

     @RequestScoped

     public FacesContext produceFacesContext() {

         return FacesContext.getCurrentInstance();

     }

     @Produces

     @RequestScoped

     public Map<String, String> getRequestParameterMap(){

         return FacesContext.getCurrentInstance().getExternalContext()

                 .getRequestParameterMap();

     } 

 }

Resources

注：该类主要用@Produces提供了CDI注入对象的实例化方法。

5、web层的Controller：MemberController

 package org.jboss.as.quickstart.hibernate4.controller;

 import java.util.List;

 import java.util.Map;

 import javax.annotation.PostConstruct;

 import javax.enterprise.inject.Model;

 import javax.enterprise.inject.Produces;

 import javax.faces.application.FacesMessage;

 import javax.faces.context.FacesContext;

 import javax.inject.Inject;

 import javax.inject.Named;

 import org.jboss.as.quickstart.hibernate4.model.Member;

 import org.jboss.as.quickstart.hibernate4.service.MemberService;

 @Model

 public class MemberController {

     @Inject

     MemberService service;

     @Inject

     private FacesContext facesContext;

     @Inject

     private Map<String, String> requestMap;

     private Member newMember;

     @Produces

     @Named

     public Member getNewMember() {

         return newMember;

     }

     @Produces

     @Named

     public List<Member> getMembers() {

         List<Member> members = null;

         try {

             members = service.getMembers();

         } catch (Exception e) {

             String errorMessage = getRootErrorMessage(e);

             facesContext.addMessage(null, new FacesMessage(

                     FacesMessage.SEVERITY_ERROR, errorMessage,

                     "Delete unsuccessful"));

         }

         return members;

     }

     public void deleteMemberById() {

         try {

             String id = requestMap.get("id");

             service.deleteMember(Long.parseLong(id));

         } catch (Exception e) {

             String errorMessage = getRootErrorMessage(e);

             facesContext.addMessage(null, new FacesMessage(

                     FacesMessage.SEVERITY_ERROR, errorMessage,

                     "Delete unsuccessful"));

         }

     }

     public void findMemberById() {

         try {

             String id = requestMap.get("id");

             newMember = service.findMember(Long.parseLong(id));

         } catch (Exception e) {

             String errorMessage = getRootErrorMessage(e);

             facesContext.addMessage(null, new FacesMessage(

                     FacesMessage.SEVERITY_ERROR, errorMessage,

                     "Find Member unsuccessful"));

         }

     }

     public void register() {

         try {

             if (newMember.getId() > 0) {

                 service.updateMember(newMember);

                 facesContext.addMessage(null, new FacesMessage(

                         FacesMessage.SEVERITY_INFO, "Updated!",

                         "Update successful"));

             } else {

                 service.addMember(newMember);

                 facesContext.addMessage(null, new FacesMessage(

                         FacesMessage.SEVERITY_INFO, "Registered!",

                         "Registration successful"));

             }

             initNewMember();

         } catch (Exception e) {

             String errorMessage = getRootErrorMessage(e);

             facesContext.addMessage(null, new FacesMessage(

                     FacesMessage.SEVERITY_ERROR, errorMessage,

                     "Save unsuccessful"));

         }

     }

     @PostConstruct

     public void initNewMember() {

         newMember = new Member();

     }

     private String getRootErrorMessage(Exception e) {

         String errorMessage = "Registration failed. See server log for more information";

         if (e == null) {

             return errorMessage;

         }

         Throwable t = e;

         while (t != null) {

             errorMessage = t.getLocalizedMessage();

             t = t.getCause();

         }

         return errorMessage;

     }

 }

MemberController

6、UI界面index.xhtml

 <?xml version="1.0" encoding="UTF-8"?>

 <ui:composition xmlns="http://www.w3.org/1999/xhtml"

     xmlns:ui="http://java.sun.com/jsf/facelets"

     xmlns:f="http://java.sun.com/jsf/core"

     xmlns:h="http://java.sun.com/jsf/html"

     template="/WEB-INF/templates/default.xhtml">

     <ui:define name="content">

         <h:form id="reg">

             <h2>Member Registration</h2>

             <h:panelGrid columns="3" width="100%" columnClasses="titleCell">

                 <h:inputHidden value="#{newMember.id}" id="id" />

                 <h:outputLabel for="name" value="Name:" />

                 <h:inputText id="name" value="#{newMember.name}" />

                 <h:message for="name" errorClass="invalid" />

                 <h:outputLabel for="email" value="Email:" />

                 <h:inputText id="email" value="#{newMember.email}" />

                 <h:message for="email" errorClass="invalid" />

                 <h:outputLabel for="phoneNumber" value="Phone #:" />

                 <h:inputText id="phoneNumber" value="#{newMember.phoneNumber}" />

                 <h:message for="phoneNumber" errorClass="invalid" />

                 <h:outputLabel for="address" value="Address:" />

                 <h:inputText id="address" value="#{newMember.address}" />

                 <h:message for="address" errorClass="invalid" />

             </h:panelGrid>

             <h:panelGrid columns="2">

                 <h:commandButton id="register" action="#{memberController.register}"

                     value="Register" styleClass="register" />

                 <h:messages styleClass="messages" errorClass="invalid"

                     infoClass="valid" warnClass="warning" globalOnly="true" />

             </h:panelGrid>

         </h:form>

         <h2>Members</h2>

         <h:panelGroup rendered="#{empty members}">

             <em>No registered members.</em>

         </h:panelGroup>

         <h:dataTable var="_member" value="#{members}"

             rendered="#{not empty members}" styleClass="simpletablestyle">

             <h:column>

                 <f:facet name="header">Id</f:facet>

                 #{_member.id}

             </h:column>

             <h:column>

                 <f:facet name="header">Name</f:facet>

                 #{_member.name}

             </h:column>

             <h:column>

                 <f:facet name="header">Email</f:facet>

                 #{_member.email}

             </h:column>

             <h:column>

                 <f:facet name="header">Phone #</f:facet>

                 #{_member.phoneNumber}

             </h:column>

             <h:column>

                 <f:facet name="header">Address</f:facet>

                 #{_member.address}

             </h:column>

             <h:column>

                 <f:facet name="header">Operation</f:facet>

                 <h:form style="border:none">

                     <h:commandLink action="#{memberController.deleteMemberById}"

                         value="delete">

                         <f:param name="id" value="#{_member.id}"></f:param>

                     </h:commandLink>|

                 <h:commandLink action="#{memberController.findMemberById}"

                         value="update">

                         <f:param name="id" value="#{_member.id}"></f:param>

                     </h:commandLink>

                 </h:form>

             </h:column>

         </h:dataTable>

     </ui:define>

 </ui:composition>

index.xhtml

7、persistence.xml 配置文件

 <?xml version="1.0" encoding="UTF-8"?>

 <persistence version="2.0"

     xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

     xsi:schemaLocation="

         http://java.sun.com/xml/ns/persistence

         http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">

     <persistence-unit name="primary">

         <jta-data-source>java:/XE</jta-data-source>

         <mapping-file>META-INF/orm.xml</mapping-file>

         <properties>

             <property name="hibernate.hbm2ddl.auto" value="create-drop" />

             <property name="hibernate.show_sql" value="true" />

             <property name="hibernate.format_sql" value="true" />

             <property name="hibernate.use_sql_comments" value="true"/>

         </properties>

     </persistence-unit>

 </persistence>

persistence.xml

注：该文件位于src/main/resources/META-INF/目录下。java:/XE 是Jboss上配置好的一个数据源JNDI字符串。hibernate.hbm2ddl.auto属性值为create-drop，表明webapp启动时，会自动在db中创建表、序列对象，webapp停止时这些对象会自动drop

8、db初始化脚本 import.sql （测试的时候十分有用）

 insert into MemberHibernate4Demo (id, name, email, phone_number, address) values (SEQ_MEMBER.NEXTVAL, 'John Smith', 'john.smith@mailinator.com', '2125551212', 'Boston NY')

 insert into MemberHibernate4Demo (id, name, email, phone_number, address) values (SEQ_MEMBER.NEXTVAL, 'Madhumita Sadhukhan', 'msadhukh@gmail.com', '2135551214', 'Brno CZ')

import.sql

注：该文件位于src/main/resources目录下，webapp启用时将自动执行该文件中的db 脚本

9、其它运行准备：
9.1 要有Oracle Database环境，比如本机可以安装一个Express版本

9.2 Jboss中要配置一个java:/XE的数据源，步骤:

a) 先部署ojdbc6.jar （这是oracle驱动，安装oracle XE或client后，本机安装目录下就能找到）

b) 添加oracle 数据源，数据库驱动选择ojdbc6.jar，连接串参考 jdbc:oracle:thin:@localhost:1521:XE

示例程序下载：http://files.cnblogs.com/yjmyzz/jboss-jpa-sample.zip

运行截图：

码农公寓

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