ibatis多表关联查询

流程：

1、创建pojo类（在一对多关联关系中，应该在“一”这端的pojo有一个“多”这一端的引用，而多这端有一这端的集合引用（即聚合关联）

2、创建pojo对应的数据库表，并插入数据

3、在ibatis配置文件中配置pojo类（配置方法：SqlMappingConfig.xml文件中添加如<typeAlias alias="Key" type="com.longsky.ibatis.lock.model.Key"/>配置，下文会看到。）

4、在pojo对应的xml配置文件中配置resultMap，比如在Lock.xml文件中添加

<resultMap id="LockResult" class="Lock">   
  <result property="id" column="id"/> <result property="lockName" column="lockName"/>   
  <result property="keys" column="id" select="getKeysByLockId"/>   
  </resultMap>

5、在需要级联查询的查询语句中使用resultMap，比如

<select id="selectAllLocks" resultMap="LockResult">   
  <![CDATA[   
  select id,lockName from lock
  ]]>   
  </select>   

上面的resultMap="LockResult"就是使用resultMap

下面进行详细介绍：

这里用表lock和key为例,一个lock可以配多个key,一个key只能对应一个lock.
数据库表

创建lock表

create table tlock(

id varchar(2) not null,
lockName varchar(10),

primary key(id));

创建key表

create table tkey(

id varchar(2) not null primary key,
lockid varchar(2) not null,
keyName varchar(10),

foreign key(lockid) references tlock(id));

插入数据到两个表：

insert into tlock values('1','drawer1');
insert into tlock values('2','drawer2');

insert into tkey values('1','1','key1');
insert into tkey values('2','1','key2');
insert into tkey values('1','2','key3');
insert into tkey values('2','2','key4');

定义映射类:

key持久化类：

public class Key {
  
 private int id;
 private int lockId;
  private String keyName;
  private Lock lock;

 public int getId() {
  return id;
 }
 public void setId(int id) {
  this.id = id;
 }
 public int getLockId() {
  return lockId;
 }
 public void setLockId(int lockId) {
  this.lockId = lockId;
 }
 public String getKeyName() {
  return keyName;
 }
 public void setKeyName(String keyName) {
  this.keyName = keyName;
 }
 public Lock getLock() {
  return lock;
 }
 public void setLock(Lock lock) {
  this.lock = lock;
 }
 
}

Lock持久化类:

public class Lock {

private int id;
private String lockName;
private List<Key> keys; 

 public int getId() {
   return id;
  }
  public void setId(int id) {
   this.id = id;
  }
  public String getLockName() {
   return lockName;
  }
  public void setLockName(String lockName) {
   this.lockName = lockName;
  }
  public List<Key> getKeys() {
   return keys;
  }
  public void setKeys(List<Key> keys) {
   this.keys = keys;
  }
}

配置ibatis的 SqlMapping文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE sqlMap PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"
   "http://ibatis.apache.org/dtd/sql-map-2.dtd">

<sqlMap namespace="lock">   
  
<typeAlias alias="Key" type="com.longsky.ibatis.lock.model.Key"/>   
  <typeAlias alias="Lock" type="com.longsky.ibatis.lock.model.Lock"/>   
    
  <resultMap id="KeyResult" class="Key">   
  <result property="id" column="id"/>   
  <result property="keyName" column="keyName"/>   
  <result property="lock" column="lockId" select="getLockById"/>   
  </resultMap>
  <!-- 通过key表中保存的lock的id实现的一对一关联,ibatis会使用getLockById(lockId)的结果填充lock属性 -->
    
  <resultMap id="LockResult" class="Lock">   
  <result property="id" column="id"/>   
  <result property="lockName" column="lockName"/>   
  <result property="keys" column="id" select="getKeysByLockId"/>   
  </resultMap>
  <!-- 通过lock表中的id实现的一对多关联,ibatis会使用getKeysByLockId(id)得到的List填充keys属性 -->
  
  <select id="selectAllkeys" resultMap="KeyResult">   
  <!--[CDATA[   
  select id,lockId,keyName from lock_key_table
  ]]>   
  </select>    
    
  <select id="getLockById" parameterClass="int" resultClass="Lock">   
  <![CDATA[   
  select id,lockName from lock where id = #value#   
  ]]>   
  </select>
  
  <select id="selectAllLocks" resultMap="LockResult">   
  <![CDATA[   
  select id,lockName from lock
  ]]>   
  </select>   
    
  <select id="getKeysByLockId" parameterClass="int" resultClass="key">   
  <![CDATA[   
  select id,lockId,keyName from lock_key_table where lockId = #value#   
  ]]-->   
  </select>
  
 </sqlMap>  

写测试类:

import java.io.IOException;
import java.io.Reader;
import java.sql.SQLException;
import java.util.List;
import com.ibatis.common.resources.Resources;
import com.ibatis.sqlmap.client.SqlMapClient;
import com.ibatis.sqlmap.client.SqlMapClientBuilder;
import com.longsky.ibatis.lock.model.Key;
import com.longsky.ibatis.lock.model.Lock;

public class Test {

 @SuppressWarnings("unchecked")
 public static void main(String[] args) throws SQLException {
  SqlMapClient sqlMapper=null ;
  try{
         Reader reader = Resources.getResourceAsReader("SqlMapConfig.xml");
         sqlMapper = SqlMapClientBuilder.buildSqlMapClient(reader);
         reader.close(); 
         }
     catch(IOException e){
         throw new RuntimeException("Something bad happened while building the SqlMapClient instance." + e, e);
         }
      List<Lock> locks=(List<Lock>)sqlMapper.queryForList("selectAllLocks");
      //取Lock对象。
      for(int i=0;i<locks.size();i++){
      Lock lock=(Lock)locks.get(i);
      System.out.println("lock name = ["+lock.getLockName()+"] has keys as follows:");
      //从Lock对象取List<Key>。
      List<Key> keys=lock.getKeys();
      for(int j=0;j<keys.size();j++){
       System.out.println("key"+j+":"+keys.get(i).getKeyName());
      }
    }
 }
}

来源：http://www.codesky.net/article/201108/106032.html

相关文章：http://www.cnblogs.com/j2eedesigner/archive/2011/09/18/2180285.html