ssh（struts2+spring+hibernate）+mybatis，用mybatis做多表查询

上篇说的是集成和用mybatis做的简单查询，那么这篇说的是多表查询。

试了好几个方法，说下最终成功的方法。

1.数据库新建2个表.

　　新建表Test和表Test1。表的结构一样，如下所示。



2.在src/com/A/B/persistence 新建文件Test.java（对应数据表Test）和ABPO.java（对应2表连接查询结果）,对应数据表Test1的文件，在本例没有使用到，可不建。

Test.java

public class Test {
private String id;
private String username;
private String password;

public Test(){}

public String getId() {
return id;
}
public void setId(String 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;
}

public String toString(){
return "Test[id="+id+" , username="+username+" , password="+password+"]";
}

}

ABPO.java

public class ABPO {
private String aid;
private String ausername;
private String apassword;
private String busername;
private String bpassword;

public ABPO(){}

public String getAid() {
return aid;
}

public void setAid(String aid) {
this.aid = aid;
}

public String getAusername() {
return ausername;
}

public void setAusername(String ausername) {
this.ausername = ausername;
}

public String getApassword() {
return apassword;
}

public void setApassword(String apassword) {
this.apassword = apassword;
}

public String getBusername() {
return busername;
}

public void setBusername(String busername) {
this.busername = busername;
}

public String getBpassword() {
return bpassword;
}

public void setBpassword(String bpassword) {
this.bpassword = bpassword;
}

}

3.在src/com/A/B/dao 建接口和xml文件

TestDAO.java

public interface  TestDAO  {
public Test getTest(Test test);
public void addTest(Test test);
public void updateTest(Test test);
public void deleteTest(int id);
List<ABPO> selectUnion(String id,String name);
}

TestDAO.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.A.B.dao.TestDAO">
<select id="getTest" parameterType="com.A.B.persistence.Test" resultType="com.A.B.persistence.Test">
SELECT * FROM test WHERE username=#{username} AND password=#{password}
</select>

<insert id="addTest" parameterType="com.A.B.persistence.Test" flushCache="true">
INSERT INTO test (id,username,password) VALUES (#{id},#{username},#{password})
</insert>

<update id="updateTest" parameterType="com.A.B.persistence.Test">
UPDATE test SET password=#{password} WHERE id=#{id}
</update>

<delete id="deleteTest" parameterType="int">
DELETE FROM test WHERE id=#{id}
</delete>

<resultMap type="com.A.B.persistence.ABPO" id="lt">
<result property="aid" column="id"/>
<result property="ausername" column="ausername"/>
<result property="apassword" column="apassword"/>
<result property="busername" column="busername"/>
<result property="bpassword" column="bpassword"/>
</resultMap>

<select id="selectUnion"  resultMap="lt">
select  a.id as aid,a.username as ausername,a.password apassword,b.username as busername,b.password bpassword
from test a
LEFT JOIN test1 b on a.id=b.id
where a.id=#{0} and  a.username=#{1}
</select>

</mapper>

4. 最后一步，测试

ApplicationContext ctx=new ClassPathXmlApplicationContext("applicationContext.xml");
TestDAO testDAO=(TestDAO)ctx.getBean("testDAO");
List<ABPO> obj=testDAO.selectUnion("1","Jessica1");

如果Test表里有id为“1”的数据，那么使用testDAO.selectUnion("1","Jessica1")会查询到一条信息，如果Test表里没有,则查询不到。

当然也可以将TestDAO.java里的selectUnion方法的参数去掉，同时去掉TestDAO.xml里的selectUnion 的where语句，那么查询的是test表里所有的信息。