JPA 多对一单向

 

http://ningnian169.blog.51cto.com/2417825/452825

 

 

自己做了一个单向多对一的例子。

     主贴类(1)-----回帖类(m)

     Topic(1)------Feedback(m)

      persistence.xml

<?xml version="1.0" encoding="UTF-8"?> 
<persistence version="1.0" 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_1_0.xsd"> 
    <persistence-unit name="JpaTest" transaction-type="RESOURCE_LOCAL"> 
    <provider>org.hibernate.ejb.HibernatePersistence</provider> 
    <class>com.entity.Topic</class> 
    <class>com.entity.Feedback</class> 
    <exclude-unlisted-classes>true</exclude-unlisted-classes> 
    <properties> 
        <property name="hibernate.connection.driver_class" value="oracle.jdbc.driver.OracleDriver"/> 
        <property name="hibernate.connection.url" value="jdbc:oracle:thin:@localhost:1521:orcl"/> 
        <property name="hibernate.connection.username" value="ningnian"/> 
        <property name="hibernate.connection.password" value="ningningx"/> 
        <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect"/> 
        <property name="hibernate.show_sql" value="true" /> 
        <property name="hibernate.hbm2ddl.auto" value="update"/>          
    </properties> 
    </persistence-unit> 
</persistence> 
TopicEntity
 
 
package com.entity;  
 
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.Table;  
 
@Entity 
@Table 
public class Topic implements Serializable {  
 
    /** 
     *  
     */ 
    private static final long serialVersionUID = 1L;  
 
    private int id;  
    private String author;  
    private String title;  
    private String context;  
 
    @Id 
    @Column 
    @GeneratedValue(strategy = GenerationType.AUTO)  
    public int getId() {  
        return id;  
    }  
 
    public void setId(int id) {  
        this.id = id;  
    }  
 
    @Column(length = 20)  
    public String getAuthor() {  
        return author;  
    }  
 
    public void setAuthor(String author) {  
        this.author = author;  
    }  
 
    @Column(length = 20)  
    public String getTitle() {  
        return title;  
    }  
 
    public void setTitle(String title) {  
        this.title = title;  
    }  
 
    @Column(length = 20)  
    public String getContext() {  
        return context;  
    }  
 
    public void setContext(String context) {  
        this.context = context;  
    }  
 
}  
Feedback
 
 
package com.entity;  
 
import java.io.Serializable;  
 
import javax.persistence.CascadeType;  
import javax.persistence.Column;  
import javax.persistence.Entity;  
import javax.persistence.FetchType;  
import javax.persistence.GeneratedValue;  
import javax.persistence.GenerationType;  
import javax.persistence.Id;  
import javax.persistence.JoinColumn;  
import javax.persistence.ManyToOne;  
 
@Entity 
public class Feedback implements Serializable {  
 
    /** 
     *  
     */ 
    private static final long serialVersionUID = 1L;  
 
    private int id;  
    private String author;  
    private String context;  
    private Topic topics;  
 
    @Id 
    @Column 
    @GeneratedValue(strategy = GenerationType.AUTO)  
    public int getId() {  
        return id;  
    }  
 
    public void setId(int id) {  
        this.id = id;  
    }  
 
    @Column 
    public String getAuthor() {  
        return author;  
    }  
 
    public void setAuthor(String author) {  
        this.author = author;  
    }  
 
    @Column 
    public String getContext() {  
        return context;  
    }  
 
    public void setContext(String context) {  
        this.context = context;  
    }  
 
    /** 
     * cascade = CascadeType.MERGE--级联更新 cascade=CascadeType.PERSIST--级联持久 
     * cascade=CascadeType.REMOVE--级联删除 cascade=CascadeType.REFRESH-- 
     * 级联刷新--在业务逻辑中可能对象进行修改，但是读取出来并不是最新的数据。 如果需要最新的数据，这时就得需要级联刷新 fetch = 
     * FetchType.LAZY--开启延迟加载。 fetch = FetchType.EAGER--即时加载 optional--boolean 
     * 在数据中，这个字段是否为空 optional=false,这个选项不可以空 
     */ 
    @ManyToOne(cascade = CascadeType.REFRESH, fetch = FetchType.LAZY, optional = false)  
    /** 
     * @JoinColumn(name = "top_id") 指定外键 
     */ 
    @JoinColumn(name = "top_id")  
    public Topic getTopics() {  
        return topics;  
    }  
 
    public void setTopics(Topic topics) {  
        this.topics = topics;  
    }  
 
}

测试类

 

@Test 
    public void testFeedback() {  
        EntityManagerFactory factory = Persistence  
                .createEntityManagerFactory("JpaTest");  
        EntityManager manager = factory.createEntityManager();  
 
        Topic topic = new Topic();  
        topic.setTitle("test");  
        topic.setContext("this is test");  
        topic.setAuthor("ning");  
 
        Feedback fk = new Feedback();  
        fk.setAuthor("nian");  
        fk.setContext("________");  
        fk.setTopics(topic);  
 
        manager.getTransaction().begin();  
        manager.persist(fk);  
        manager.getTransaction().commit();  
 
    }