我做了一个mybatis的demo里面有两个类：user address，user中存放着一个address，而在数据库中user表中有一个addressid的字段，用于关联address表。
public class User {
private int id;
private String name;
private String password;
private int age;
private Address address;
//get set方法
}
public class Address {
private int addid;
private String addname;
private int zipcode;
//get set方法
}
mybatis配置文件
<!-- 延迟加载设置 -->
<settings>
<setting name="lazyLoadingEnabled" value="true"/>
</settings>
<!-- 别名 -->
<typeAliases>
<typeAlias type="com.qshun.model.User" alias="user"/>
<typeAlias type="com.qshun.model.Address" alias="address"/>
</typeAliases>
<!-- 环境参数（数据库连接） -->
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver" />
<property name="url" value="jdbc:mysql://localhost/ibatis" />
<property name="username" value="root" />
<property name="password" value="root" />
</dataSource>
</environment>
</environments>
<!-- 映射文件 -->
<mappers>
<mapper resource="com/qshun/model/AddressMapper.xml"/>
<mapper resource="com/qshun/model/UserMapper.xml"/>
</mappers>
usermapper的实体映射文件
<resultMap type="user" id="UserResultMap">
<result property="id" column="uid" />
<result property="name" column="uname" />
<result property="password" column="upassword" />
<result property="age" column="uage" />
<association property="address" column="addressid" select="getAddressById" resultMap="AddressResultMap">
</association>
</resultMap>
<resultMap id="AddressResultMap" type="address">
<result property="addid" column="id"/>
<result property="addname" column="addressname"/>
<result property="zipcode" column="zipcode"/>
</resultMap>
<select id="getUserById" resultMap="UserResultMap" parameterType="int">
select uid,uname,upassword,uage,addressid
from user
where uid=#{id}
</select>
<select id="getAddressById" resultMap="AddressResultMap">
select addid, addname, zipcode
from addr
where addid =#{addressid}
</select>
测试类
private static SqlSession session = null;
private static SqlSessionFactory sqlSessionFactory = null;
static {
try {
Reader reader = Resources.getResourceAsReader("MybatisConfig.xml");
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
session = sqlSessionFactory.openSession(true);
reader.close();
} catch (IOException e) {
throw new RuntimeException("=========" + e, e);
}
}
public static void main(String[] args) {
UserMapper mapper=session.getMapper(UserMapper.class);
User u=mapper.getUserById(1);//理论上讲在执行此操作的时候，不会将address对象查询出来
System.out.println(u.getName());
System.out.println("================");
System.out.println(u.getAddress().getAddname());//此时address才会被执行查询
//但是事实上在执行mapper.getUserById(1)的时候，就执行了address对象的查询，延迟加载没有起效
session.close();
}
另附建表语句
CREATE TABLE ibatis.add (addid INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,addname VARCHAR(45),zipcode VARCHAR(45),
PRIMARY KEY (addid)
)
ENGINE = InnoDB;
CREATE TABLE ibatis.user (uid INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,uname VARCHAR(45),upassword VARCHAR(45),uage VARCHAR(45),addressid VARCHAR(45),
PRIMARY KEY (uid)
)
ENGINE = InnoDB;
请各位牛人，帮忙解答一下，不胜感激 :D
你的代码存在问题。
1、
setting文件这样配置
只有这两个属性都配置了才能生效！
2、下面的映射也有问题，我就不更正了，给你个例子参考
<select id="getStudentById" parameterType="int" resultMap="studentResultMap2">
SELECT id,name,classid
FROM student s
WHERE s.id=#{id}
</select>
<select id="getClassesById" parameterType="int" resultType="classes">
SELECT id,name
FROM classes c
WHERE c.id=#{id}
</select>
3、我有空会把这个demo代码放到我的博客中，要是还是搞不定你再看看。
[quote]UserMapper mapper=session.getMapper(UserMapper.class);
User u=mapper.getUserById(1);//理论上讲在执行此操作的时候，不会将address对象查询出来
System.out.println(u.getName());
System.out.println("================");
System.out.println(u.getAddress().getAddname());//此时address才会被执行查询
//但是事实上在执行mapper.getUserById(1)的时候，就执行了address对象的查询，延迟加载没有起效
session.close(); [/quote]
请问你把这查找用户和查找地址写在一段程序里面，是如何判断它有没有延迟加载的呢？是通过日志输出是否在“=========”前面来查看的吗？
为什么要用association标签？
不是应该也用result的么？