ibatis-多表关联查询

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

写道

create table lock(
id int,
lockName varchar
);
create table key(
id int,
lockId int,
keyName varchar
);

 定义映射类:

写道

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;
}

}
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

写道

<?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:

写道

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());
}
}
}
}