本文将接着上文，讲解hibernate4的集合映射的注解和关联关系映射的注解。本文包括两个部分：

1. 集合映射的注解。
2. 关联关系映射的注解。

一、集合映射的注解

         当持久化中有一个属性是集合(Set、List、Map)，就要用到集合映射。集合属性会单独生成一张表。定义集合属性时面向接口，并且集合属性需要程序员自己初始化（例如：private List<String> list = new ArrayList<String>();）。

集合属性都要用到的注解：

• @ElementCollection(fetch="该属性的加载策略"，targetClass="集合中元素的类型")。
  fetch=FetchType.EAGER: 立即加载
  fetch=FetchType.LAZY: 延迟加载
• @CollectionTable(name="表名") : 指定集合生成表的相关信息。

1.1 List集合映射(有序集合): @OrderColumn() 指定排序列

注意：List集合生成表的主键列：（外键列 + 排序列）

1.1.1 List<String> : 集合中元素是标量类型 8个基本类型、包装类、String。

例如：Employee类

package edu.scut.e_CollectionMapping_List;import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import javax.persistence.*;@Entity
@Table(name="EMP_INFO")
public class Employee implements Serializable {@Id@GeneratedValue(strategy=GenerationType.AUTO)private int id;private String name;private int age;@ElementCollection(fetch=FetchType.LAZY, //加载策略,延迟加载targetClass=String.class) //指定集合中元素的类型@CollectionTable(name="ADD_INFO") //指定集合生成的表@OrderColumn(name="O_ID") //指定排序列的名称private List<String> address = new ArrayList<String>();public int getId() {return id;}public List<String> getAddress() {return address;}public void setAddress(List<String> address) {this.address = address;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}
}

生成两张表：

emp_info表

add_info表

1.1.2 List<Address> : 集合中元素是复合类型。复合属性类上需要加注解：@Embeddable。

例如：Person类

package edu.scut.e_CollectionMapping_List;import java.util.ArrayList;
import java.util.List;
import javax.persistence.*;@Entity
@Table(name="PER_INFO")
public class Person {@Id@GeneratedValue(strategy=GenerationType.AUTO)private int id;private String name;@ElementCollection(fetch=FetchType.LAZY, //加载策略targetClass=Address.class) //指定元素中集合的类型@CollectionTable(name="PER_ADD_INFO") //指定集合生成的表@OrderColumn(name="O_A_ID") //指定排序列的名称private List<Address> address = new ArrayList<Address>();public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public List<Address> getAddress() {return address;}public void setAddress(List<Address> address) {this.address = address;}
}

Address类

package edu.scut.e_CollectionMapping_List;import javax.persistence.Embeddable;@Embeddable
public class Address {private String zip;private String info;public String getZip() {return zip;}public void setZip(String zip) {this.zip = zip;}public String getInfo() {return info;}public void setInfo(String info) {this.info = info;}
}

生成的两张表：

per_info表

per_add_info表

1.2 Set集合映射(无序集合)

注意： Set集合生成表的主键列：（外键列 + Set集合的元素列 .. ）

1.2.1· Set<String> : 集合中元素是标量类型 8个基本类型、包装类、String。

           Set集合生成表默认是没有主键列的。如果想要生成主键列，需要为Set集合添加非空约束！

例如：Employee类

package edu.scut.e_CollectionMapping_Set;import java.io.Serializable;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import javax.persistence.*;@Entity
@Table(name="EMP_INFO")
public class Employee implements Serializable {@Id@GeneratedValue(strategy=GenerationType.AUTO)private int id;private String name;private int age;@ElementCollection(fetch=FetchType.LAZY, //加载策略,延迟加载targetClass=String.class) //指定集合中元素的类型@CollectionTable(name="ADD_INFO") //指定集合生成的表@Column(nullable=false) //添加非空约束private Set<String> address = new HashSet<String>();public int getId() {return id;}public Set<String> getAddress() {return address;}public void setAddress(Set<String> address) {this.address = address;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}
}

1.2.2  Set<Address> : 集合中元素是复合类型。
          复合属性类上需要加注解：@Embeddable
         Set集合生成表默认是没有主键列的。如果想要生成主键列，需要为Set集合的元素类的属性上添加非空约束！

例如：Person类

package edu.scut.e_CollectionMapping_Set;import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import javax.persistence.*;@Entity
@Table(name="PER_INFO")
public class Person {@Id@GeneratedValue(strategy=GenerationType.AUTO)private int id;private String name;@ElementCollection(fetch=FetchType.LAZY, //加载策略targetClass=Address.class) //指定元素中集合的类型@CollectionTable(name="PER_ADD_INFO") //指定集合生成的表private Set<Address> address = new HashSet<Address>();public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Set<Address> getAddress() {return address;}public void setAddress(Set<Address> address) {this.address = address;}
}

Address类

package edu.scut.e_CollectionMapping_Set;import javax.persistence.Column;
import javax.persistence.Embeddable;@Embeddable
public class Address {//@Column(nullable=false)private String zip;@Column(nullable=false)private String info;public String getZip() {return zip;}public void setZip(String zip) {this.zip = zip;}public String getInfo() {return info;}public void setInfo(String info) {this.info = info;}
}

1.3 Map集合映射(有Map的key)： @MapKeyColumn() 指定Map的key生成的列

注意： Map集合生成表的主键列：（外键列 + Map的Key）

1.3.1 Map<String, String> : 集合中元素是标量类型 8个基本类型、包装类、String。

例如：Employee类

package edu.scut.e_CollectionMapping_Map;import java.io.Serializable;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.persistence.*;@Entity
@Table(name="EMP_INFO")
public class Employee implements Serializable {@Id@GeneratedValue(strategy=GenerationType.AUTO)private int id;private String name;private int age;@ElementCollection(fetch=FetchType.LAZY, //加载策略,延迟加载targetClass=String.class) //指定集合中元素的类型@CollectionTable(name="ADD_INFO") //指定集合生成的表@MapKeyColumn(name="M_KEY") //指定map的key生成的列private Map<String, String> address = new HashMap<String, String>();public int getId() {return id;}public Map<String, String> getAddress() {return address;}public void setAddress(Map<String, String> address) {this.address = address;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}
}

1.3.2 Map<String, Address> : 集合中元素是复合类型。
         复合属性类上需要加注解：@Embeddable

例如：Person类

package edu.scut.e_CollectionMapping_Map;import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import javax.persistence.*;@Entity
@Table(name="PER_INFO")
public class Person {@Id@GeneratedValue(strategy=GenerationType.AUTO)private int id;private String name;@ElementCollection(fetch=FetchType.LAZY, //加载策略targetClass=Address.class) //指定元素中集合的类型@CollectionTable(name="PER_ADD_INFO") //指定集合生成的表@MapKeyColumn(name="ADD_KEY") //指定key生成的列private Map<String,Address> address = new HashMap<String,Address>();public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Map<String,Address> getAddress() {return address;}public void Address(Map<String,Address> address) {this.address = address;}
}

Address类

package edu.scut.e_CollectionMapping_Map;import javax.persistence.Column;
import javax.persistence.Embeddable;@Embeddable
public class Address {//@Column(nullable=false)private String zip;@Column(nullable=false)private String info;public String getZip() {return zip;}public void setZip(String zip) {this.zip = zip;}public String getInfo() {return info;}public void setInfo(String info) {this.info = info;}
}

二、关联关系映射的注解（重点）

单向关联映射和双向关联映射的最大区别就是在查询数据时，单向关联只能通过一边进行查询，而双向关联两边都可以互相查询。

2.1 单向关联映射（一边配置）

2.1.1 一对一

/** 一方*/
@OneToOne(fetch=FetchType.LAZY,cascade=CascadeType.ALL,targetEntity=Persons.class)  //维护关联关系（从表）
/** 生成外键列*/
@JoinColumn(name="P_ID",unique=true,referencedColumnName="id")

通过公民（Person）和身份证(IdCards)的例子来说明：

Person.java

package edu.scut.f_AssoMap_single_one2one;import javax.persistence.*;//公民（一方）
@Entity
@Table(name="PER_INFO")
public class Persons {@Id@GeneratedValue(strategy=GenerationType.AUTO)private int id;private String name;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}
}

IdCards.java

package edu.scut.f_AssoMap_single_one2one;import javax.persistence.*;//身份证（一方）
@Entity
@Table(name="IDCD_INFO")
public class IdCards {@Id@GeneratedValue(strategy=GenerationType.AUTO)@Column(name="IDCD_ID")private int id;private String cardno;/** 一方*/@OneToOne(fetch=FetchType.LAZY,cascade=CascadeType.ALL,targetEntity=Persons.class)  //维护关联关系（从表）/** 生成外键列*/@JoinColumn(name="P_ID",unique=true,referencedColumnName="id")private Persons persons;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getCardno() {return cardno;}public void setCardno(String cardno) {this.cardno = cardno;}public Persons getPersons() {return persons;}public void setPersons(Persons persons) {this.persons = persons;}
}

2.1.2 一对多

/** 一方*/@OneToMany(fetch=FetchType.LAZY, //延迟加载targetEntity=Orders.class, //目标对象cascade=CascadeType.ALL,//级联操作orphanRemoval=true)  //孤儿删除@JoinColumn(name="C_ID",referencedColumnName="CUS_ID")

通过客户（Customers）和订单(Orders)的例子说明：

Customers.java

package edu.scut.f_AssoMap_single_one2n;import java.util.HashSet;
import java.util.Set;
import javax.persistence.*;//客户（一方）
@Entity
@Table(name="CUS_INFO")
public class Customers {@Id@GeneratedValue(strategy=GenerationType.AUTO)@Column(name="CUS_ID")private int id;private String name;/** 一方*/@OneToMany(fetch=FetchType.LAZY, //延迟加载targetEntity=Orders.class, //目标对象cascade=CascadeType.ALL,//级联操作orphanRemoval=true)  //孤儿删除@JoinColumn(name="C_ID",referencedColumnName="CUS_ID")private Set<Orders> orders = new HashSet<Orders>();public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Set<Orders> getOrders() {return orders;}public void setOrders(Set<Orders> orders) {this.orders = orders;}
}

Orders.java

package edu.scut.f_AssoMap_single_one2n;import javax.persistence.*;;
import javax.persistence.Table;//订单（多方）
@Entity
@Table(name="ORD_INFO")
public class Orders {@Id@GeneratedValue(strategy=GenerationType.AUTO)private int id;private String orderno;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getOrderno() {return orderno;}public void setOrderno(String orderno) {this.orderno = orderno;}
}

2.1.3 多对一

/** 多方*/@ManyToOne(fetch=FetchType.LAZY,cascade=CascadeType.ALL,targetEntity=Customers.class)
/** 生成外键列*/
@JoinColumn(name="C_ID",referencedColumnName="CUS_ID")

通过客户（Customers）和订单(Orders)的例子说明：

Customers.java

package edu.scut.f_AssoMap_single_n2one;import java.util.HashSet;
import java.util.Set;
import javax.persistence.*;//客户（一方）
@Entity
@Table(name="CUS_INFO")
public class Customers {@Id@GeneratedValue(strategy=GenerationType.AUTO)@Column(name="CUS_ID")private int id;private String name;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}
}

Orders.java

package edu.scut.f_AssoMap_single_n2one;import javax.persistence.*;//订单（多方）
@Entity
@Table(name="ORD_INFO")
public class Orders {@Id@GeneratedValue(strategy=GenerationType.AUTO)private int id;private String orderno;/** 多方*/@ManyToOne(fetch=FetchType.LAZY,cascade=CascadeType.ALL,targetEntity=Customers.class)/** 生成外键列*/@JoinColumn(name="C_ID",referencedColumnName="CUS_ID")private Customers customers;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getOrderno() {return orderno;}public void setOrderno(String orderno) {this.orderno = orderno;}public Customers getCustomers() {return customers;}public void setCustomers(Customers customers) {this.customers = customers;}}

2.1.4 多对多

/** 多方*/
@ManyToMany(fetch=FetchType.LAZY, //延迟加载cascade=CascadeType.ALL,targetEntity=Teacher.class) //目标对象
/** 中间表*/
@JoinTable(name="TEA_STU", //指定中间表名称joinColumns=@JoinColumn(name="S_ID",referencedColumnName="STU_ID"), //@ManyToMany中没有加mappedby的主键列inverseJoinColumns=@JoinColumn(name="T_ID",referencedColumnName="TEA_ID")) //@ManyToMany中加mappedby的主键列	

通过老师（Teachers）和学生(Students)的例子说明：

Teachers.java

package edu.scut.f_AssoMap_single_n2n;import java.util.HashSet;
import java.util.Set;
import javax.persistence.*;//多方
@Entity
@Table(name="TEA_INFO")
public class Teacher {@Id@GeneratedValue(strategy=GenerationType.AUTO)@Column(name="TEA_ID")private int id;private String name;private String dept;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getDept() {return dept;}public void setDept(String dept) {this.dept = dept;}
}

Students.java

package edu.scut.f_AssoMap_single_n2n;import java.util.HashSet;
import java.util.Set;import javax.persistence.*;//多方
@Entity
@Table(name="STU_INFO")
public class Student {@Id@GeneratedValue(strategy=GenerationType.AUTO)@Column(name="STU_ID")private int id;private String name;private float score;/** 多方*/@ManyToMany(fetch=FetchType.LAZY, //延迟加载cascade=CascadeType.ALL,targetEntity=Teacher.class) //目标对象/** 中间表*/@JoinTable(name="TEA_STU", //指定中间表名称joinColumns=@JoinColumn(name="S_ID",referencedColumnName="STU_ID"), //@ManyToMany中没有加mappedby的主键列inverseJoinColumns=@JoinColumn(name="T_ID",referencedColumnName="TEA_ID")) //@ManyToMany中加mappedby的主键列	private Set<Teacher> teachers = new HashSet<Teacher>();public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public float getScore() {return score;}public void setScore(float score) {this.score = score;}public Set<Teacher> getTeachers() {return teachers;}public void setTeachers(Set<Teacher> teachers) {this.teachers = teachers;}
}

2.2 双向关联映射（两边同时配置）

2.2.1 一对一

一方：

/** 一方 */
@OneToOne(fetch=FetchType.LAZY,targetEntity=IdCards.class,mappedBy="persons",   //不维护关联关系（主表）cascade=CascadeType.ALL) 

另一方：

/** 一方*/
@OneToOne(fetch=FetchType.LAZY,targetEntity=Persons.class)  //维护关联关系（从表）
/** 生成外键列*/
@JoinColumn(name="P_ID",unique=true,referencedColumnName="id")

还是通过公民（Persons）和身份证(IdCards)的例子来说明：

Persons.java

package edu.scut.f_AssoMap_double_one2one;import javax.persistence.*;//公民（一方）
@Entity
@Table(name="PER_INFO")
public class Persons {@Id@GeneratedValue(strategy=GenerationType.AUTO)private int id;private String name;/** 一方 */@OneToOne(fetch=FetchType.LAZY,targetEntity=IdCards.class,mappedBy="persons",   //不维护关联关系（主表）cascade=CascadeType.ALL) private IdCards idcards;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public IdCards getIdcards() {return idcards;}public void setIdcards(IdCards idcards) {this.idcards = idcards;}
}

IdCards.java

package edu.scut.f_AssoMap_double_one2one;import javax.persistence.*;//身份证（一方）
@Entity
@Table(name="IDCD_INFO")
public class IdCards {@Id@GeneratedValue(strategy=GenerationType.AUTO)@Column(name="IDCD_ID")private int id;private String cardno;/** 一方*/@OneToOne(fetch=FetchType.LAZY,targetEntity=Persons.class)  //维护关联关系（从表）/** 生成外键列*/@JoinColumn(name="P_ID",unique=true,referencedColumnName="id")private Persons persons;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getCardno() {return cardno;}public void setCardno(String cardno) {this.cardno = cardno;}public Persons getPersons() {return persons;}public void setPersons(Persons persons) {this.persons = persons;}
}

2.2.2 一对多

一方：

/** 一方*/
@OneToMany(fetch=FetchType.LAZY, //延迟加载targetEntity=Orders.class, //目标对象cascade=CascadeType.ALL,  //级联操作orphanRemoval=true,  //孤儿删除mappedBy="customers") //指定由哪边维护关系(从表维护)

多方：

/** 多方*/@ManyToOne(fetch=FetchType.LAZY,//cascade=CascadeType.ALL,targetEntity=Customers.class)/** 生成外键列*/@JoinColumn(name="C_ID",referencedColumnName="CUS_ID")

还是通过客户（Customers）和订单(Orders)的例子说明：

Customers.java

package edu.scut.f_AssoMap_double_one2n;import java.util.HashSet;
import java.util.Set;
import javax.persistence.*;//客户（一方）
@Entity
@Table(name="CUS_INFO")
public class Customers {@Id@GeneratedValue(strategy=GenerationType.AUTO)@Column(name="CUS_ID")private int id;private String name;/** 一方*/@OneToMany(fetch=FetchType.LAZY, //延迟加载targetEntity=Orders.class, //目标对象cascade=CascadeType.ALL,  //级联操作orphanRemoval=true,  //孤儿删除mappedBy="customers") //指定由哪边维护关系(从表维护)private Set<Orders> orders = new HashSet<Orders>();public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Set<Orders> getOrders() {return orders;}public void setOrders(Set<Orders> orders) {this.orders = orders;}
}

Orders.java

package edu.scut.f_AssoMap_double_one2n;import javax.persistence.*;//订单（多方）
@Entity
@Table(name="ORD_INFO")
public class Orders {@Id@GeneratedValue(strategy=GenerationType.AUTO)private int id;private String orderno;/** 多方*/@ManyToOne(fetch=FetchType.LAZY,//cascade=CascadeType.ALL,targetEntity=Customers.class)/** 生成外键列*/@JoinColumn(name="C_ID",referencedColumnName="CUS_ID")private Customers customers;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getOrderno() {return orderno;}public void setOrderno(String orderno) {this.orderno = orderno;}public Customers getCustomers() {return customers;}public void setCustomers(Customers customers) {this.customers = customers;}}

2.2.3 多对多

多方：

/** 多方*/@ManyToMany(fetch=FetchType.LAZY, //延迟加载targetEntity=Student.class, //指定目标对象cascade=CascadeType.ALL,mappedBy="teachers") //老师不维护关联关系

另一个多方：

/** 多方*/@ManyToMany(fetch=FetchType.LAZY, //延迟加载targetEntity=Teacher.class) //目标对象/** 中间表*/@JoinTable(name="TEA_STU", //指定中间表名称joinColumns=@JoinColumn(name="S_ID",referencedColumnName="STU_ID"), //@ManyToMany中没有加mappedby的主键列inverseJoinColumns=@JoinColumn(name="T_ID",referencedColumnName="TEA_ID")) //@ManyToMany中加mappedby的主键列	

还是通过老师（Teachers）和学生(Students)的例子说明：

Teachers.java

package edu.scut.f_AssoMap_double_n2n;import java.util.HashSet;
import java.util.Set;
import javax.persistence.*;//多方
@Entity
@Table(name="TEA_INFO")
public class Teacher {@Id@GeneratedValue(strategy=GenerationType.AUTO)@Column(name="TEA_ID")private int id;private String name;private String dept;/** 多方*/@ManyToMany(fetch=FetchType.LAZY, //延迟加载targetEntity=Student.class, //目标对象cascade=CascadeType.ALL,mappedBy="teachers") //老师不维护关联关系private Set<Student> students = new HashSet<Student>();public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getDept() {return dept;}public void setDept(String dept) {this.dept = dept;}public Set<Student> getStudents() {return students;}public void setStudents(Set<Student> students) {this.students = students;}
}

Students.java

package edu.scut.f_AssoMap_double_n2n;import java.util.HashSet;
import java.util.Set;
import javax.persistence.*;//多方
@Entity
@Table(name="STU_INFO")
public class Student {@Id@GeneratedValue(strategy=GenerationType.AUTO)@Column(name="STU_ID")private int id;private String name;private float score;/** 多方*/@ManyToMany(fetch=FetchType.LAZY, //延迟加载targetEntity=Teacher.class) //目标对象/** 中间表*/@JoinTable(name="TEA_STU", //指定中间表名称joinColumns=@JoinColumn(name="S_ID",referencedColumnName="STU_ID"), //@ManyToMany中没有加mappedby的主键列inverseJoinColumns=@JoinColumn(name="T_ID",referencedColumnName="TEA_ID")) //@ManyToMany中加mappedby的主键列	private Set<Teacher> teachers = new HashSet<Teacher>();public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public float getScore() {return score;}public void setScore(float score) {this.score = score;}public Set<Teacher> getTeachers() {return teachers;}public void setTeachers(Set<Teacher> teachers) {this.teachers = teachers;}
}