Hibernate中一对一，一对多，多对多的写法

hibernate中各类对应的bean类写法

1、一对一的情况

假设我们用Address类和User类做一对一的对应
User类

package com.telek.model;import java.util.HashSet;import java.util.Set;import javax.annotation.Generated;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.OneToOne;import javax.persistence.Table;@Entity@Table(name="user")//如果表明和对象名不一致 则需要单独加上该注解public class User implements java.io.Serializable{    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    private int id;    @Column(name="username")    private String username;    @Column(name="password")    private String password;    //fetch代表数据的抓取策略lazy就是指用到了该属性才会去查询（eager刚好相反）    @OneToOne(cascade = {CascadeType.ALL},fetch = FetchType.LAZY )    private Address address=new Address();    public User(){}    public User(String username,String password){        this.username = username;        this.password = password;    }    @return the address    public Address getAddress() {        return address;    }    @param address the address to set    public void setAddress(Address address) {        this.address = address;    }    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getUsername() {        return username;    }    public void setUsername(String username) {        this.username = username;    }    public String getPassword() {        return password;    }    public void setPassword(String password) {        this.password = password;    }}

Address类

package com.telek.model;import javax.persistence.CascadeType;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;import javax.persistence.OneToOne;import javax.persistence.Table;@Entity@Table(name="address")public class Address {    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    private int id;    private String address;    @OneToOne(optional= false,fetch = FetchType.EAGER)//cascade = CascadeType.ALL,    @JoinColumn(name="uid")    private User user;    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getAddress() {        return address;    }    public void setAddress(String address) {        this.address = address;    }    public User getUser() {        return user;    }    public void setUser(User user) {        this.user = user;    }}

1、一对多的情况

假设我们用Address类和User类做一对一的对应
Address类

package com.telek.model;import javax.persistence.CascadeType;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;import javax.persistence.OneToOne;import javax.persistence.Table;@Entity@Table(name="address")public class Address {    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    private int id;    private String address;    @ManyToOne(optional= false,fetch = FetchType.EAGER)//cascade = CascadeType.ALL,    @JoinColumn(name="uid")    private User user;    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getAddress() {        return address;    }    public void setAddress(String address) {        this.address = address;    }    public User getUser() {        return user;    }    public void setUser(User user) {        this.user = user;    }}

User类

package com.telek.model;import java.util.HashSet;import java.util.Set;import javax.annotation.Generated;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.OneToMany;import javax.persistence.OneToOne;import javax.persistence.Table;@Entity@Table(name="user")//如果表明和对象名不一致 则需要单独加上该注解public class User implements java.io.Serializable{    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    private int id;    @Column(name="username")    private String username;    @Column(name="password")    private String password;    //fetch代表数据的抓取策略lazy就是指用到了该属性才会去查询（eager刚好相反）    @OneToMany(cascade = {CascadeType.ALL},mappedBy="user",fetch = FetchType.LAZY )    private Set<Address> address = new HashSet<Address>();    public User(){}    public User(String username,String password){        this.username = username;        this.password = password;    }    public Set<Address> getAddress() {        return address;    }    public void setAddress(Set<Address> address) {        this.address = address;    }    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getUsername() {        return username;    }    public void setUsername(String username) {        this.username = username;    }    public String getPassword() {        return password;    }    public void setPassword(String password) {        this.password = password;    }}

最后，附上一对多情况中Dao包类的测试方法

public void OnetoMore(){//一对多配置        Session session = sessionFactory.openSession();        User user = new User();        user.setUsername("wjw");        user.setPassword("wlf");        Address add1 =  new Address();        add1.setAddress("浙江");        Address add2 =  new Address();        add2.setAddress("北京");        add1.setUser(user);//在多的一方告诉hibernate我这个对象属于谁        add2.setUser(user);        user.getAddress().add(add1);//在少的一端告诉hibernate我可以添加谁进来        user.getAddress().add(add2);        session.beginTransaction();        session.save(user);        session.close();    }

3、多对多的情况

假设我们用Tag类和Topic类作为演示
Tag类

package com.telek.model;// Generated 2016-3-4 9:16:37 by Hibernate Tools 4.3.1.Finalimport javax.persistence.CascadeType;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.FetchType;import javax.persistence.GeneratedValue;import static javax.persistence.GenerationType.IDENTITY;import java.util.HashSet;import java.util.Set;import javax.persistence.Id;import javax.persistence.ManyToMany;import javax.persistence.OneToMany;import javax.persistence.Table;/** * Tag generated by hbm2java */@Entity@Table(name="tag"    ,catalog="springdemo")public class Tag  implements java.io.Serializable {     private Integer tagid;     private String tag;     private Set<Topic> topic=new HashSet<Topic>();    public Tag() {    }    public Tag(String tag) {       this.tag = tag;    }     @Id @GeneratedValue(strategy=IDENTITY)    @Column(name="tagid", unique=true, nullable=false)    public Integer getTagid() {        return this.tagid;    }    public void setTagid(Integer tagid) {        this.tagid = tagid;    }    @Column(name="tag")    public String getTag() {        return this.tag;    }    public void setTag(String tag) {        this.tag = tag;    }    /**     * @return the topic     */    @ManyToMany(cascade = {CascadeType.ALL},mappedBy="tag",fetch = FetchType.LAZY )    public Set<Topic> getTopic() {        return topic;    }    /**     * @param topic the topic to set     */    public void setTopic(Set<Topic> topic) {        this.topic = topic;    }}

Topic类

package com.telek.model;// Generated 2016-3-4 9:16:37 by Hibernate Tools 4.3.1.Finalimport javax.persistence.CascadeType;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.FetchType;import javax.persistence.GeneratedValue;import static javax.persistence.GenerationType.IDENTITY;import java.util.HashSet;import java.util.Set;import javax.persistence.Id;import javax.persistence.JoinColumn;import javax.persistence.JoinTable;import javax.persistence.ManyToMany;import javax.persistence.Table;/** * Topic generated by hbm2java */@Entity@Table(name="topic"    ,catalog="springdemo")public class Topic  implements java.io.Serializable {     private Integer topicid;     private String title;     private String context;     private Set<Tag> tag = new HashSet<Tag>();    public Topic() {    }    public Topic(String title, String context) {       this.title = title;       this.context = context;    }     @Id @GeneratedValue(strategy=IDENTITY)    @Column(name="topicid", unique=true, nullable=false)    public Integer getTopicid() {        return this.topicid;    }    public void setTopicid(Integer topicid) {        this.topicid = topicid;    }    @Column(name="title")    public String getTitle() {        return this.title;    }    public void setTitle(String title) {        this.title = title;    }    @Column(name="context")    public String getContext() {        return this.context;    }    public void setContext(String context) {        this.context = context;    }    /**     * @return the tag     */    @ManyToMany(cascade = {CascadeType.ALL})    @JoinTable(name="topicandtag",joinColumns=@JoinColumn(name="topicid"),inverseJoinColumns=@JoinColumn(name="tagid"))    public Set<Tag> getTag() {        return tag;    }    /**     * @param tag the tag to set     */    public void setTag(Set<Tag> tag) {        this.tag = tag;    }}

最后在Dao里面写一个方法作为演示

public void ManyToMany(){        Session session = sessionFactory.openSession();        Topic topic = new Topic();        topic.setTitle(("大保健"));        topic.setContext("来玩来玩");        Topic topic2 = new Topic();        topic2.setTitle(("大保健"));        topic2.setContext("来玩来玩呀");        Tag tag1 = new Tag();tag1.setTag("服务");        Tag tag2 = new Tag();tag2.setTag("保健");        Set<Tag> tags = new HashSet<Tag>();        tags.add(tag1);tags.add(tag2);        topic.setTag(tags);        Set<Topic> topics = new HashSet<Topic>();        topics.add(topic);        topics.add(topic2);        tag1.setTopic(topics);        tag2.setTopic(topics);        session.beginTransaction();        session.save(topic);        session.getTransaction().commit();        session.close();}

发现关系表和Tag表和Topic表都插入数据为正常
最后，附上数据库表的情况

另外，如果在topic和tag两边都加上

@ManyToMany(cascade = {CascadeType.ALL})@JoinTable(name="topicandtag",joinColumns=@JoinColumn(name="tagid"),inverseJoinColumns=@JoinColumn(name="topicid"))

即可以不用两边set关系，只用一边关联就可以两边都存入数据库