resultType:直接表示返回类型
resultMap：对外部resultMap的引用
二者不能同时使用
创建一个实体类Role和User
public class Role {private Integer id;private String roleCode;private String roleName;//省略set、get方法
创建User类（在User中有roleId 1对多关系）
public class User {private Integer id;private String userName;private String userCode;private String userPassword;private Integer roleId;private String roleName;
//省略set、get方法
创建RoleMapper接口
public interface RoleMapper {public void add(Role role);public void update(Role role);public void delete(Role role);public List<Role> getRoleList();}
创建UserMapper接口
//接口的名字和xml的名字一样，这样xml中的namespace就不用改 public interface UserMapper {//接口名的方法名一定要和xml中的id名一样public int count();public void add(User user);public void update(User user);public void delete(User user);public List<User> getUserList();//根据roleid获取用户列表public List<User> getUserByRoleId(Role role); }
创建RoleMapper.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="cn.bdqn.dao.RoleMapper"><select id="getRoleList" resultType="Role">select * from role</select><insert id="add" parameterType="Role">insert into role (roleCode,roleName) values (#{roleCode},#{roleName})</insert><update id="update" parameterType="Role">update role set roleCode=#{roleCode},roleName=#{roleName} where id=#{id}</update><delete id="delete" parameterType="Role">delete from role where id=#{id}</delete> </mapper>
创建UserMapper.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"> <!-- 如果我要调用mapper文件，就去拿到namespace+id(方法名)的名字就可以访问 --> <mapper namespace="cn.bdqn.dao.UserMapper"><!-- id要唯一的，一般是下拉类的方法名 --><!-- 返回的是什么类型int --><select id="count" resultType="int">select count(1) from user</select><!-- 增加 --><insert id="add" parameterType="User">insert into user(userCode,userName,userPassword)values (#{userCode},#{userName},#{userPassword})</insert><!-- 修改 --><update id="update" parameterType="User">update user set userCode=#{userCode},userName=#{userName},userPassword=#{userPassword} where id=#{id}</update><!-- 删除 --><delete id="delete" parameterType="User">delete from user where id=#{id}</delete><!-- 查询 --><select id="getUserList" resultType="User">select * from user</select> </mapper>
加入这个方法用resultMap
<!-- resultMap中的id随便取，但要保证id唯一就行 --><!-- type指的是后台的javabean的类名 映射到哪里 --><resultMap type="User" id="userMap"><!-- 显示的字段 --><result property="id" column="id"/><result property="userCode" column="userCode"/><result property="userName" column="userName"/><result property="roleName" column="roleName"/></resultMap><!-- 拿roleID --><select id="getUserByRoleId" parameterType="User" resultMap="userMap">select u.*,r.roleName as roleName from user u,role r where u.roleId = r.id and u.roleId=#{id}</select>
在mybatis-config.xml中添加<mapper resource="cn/bdqn/dao/RoleMapper.xml"/>
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"><!-- 通过这个配置文件完成mybatis与数据库的连接 --> <configuration><!-- 引入 jdbc.properties 文件--><properties resource="jdbc.properties"/><!-- alias别名 --><!-- 配置mybatis的log实现LOG4J --> <settings><setting name="logImpl" value="LOG4J" /> </settings><typeAliases><!-- <typeAlias type="cn.bdqn.pojo.User" alias="User"/> --><!-- 用这个比较方便，不用一个一个写。包下的就是他的类名 --><package name="cn.bdqn.pojo"/></typeAliases><environments default="development"><environment id="development"><!--配置事务管理，采用JDBC的事务管理 --><transactionManager type="JDBC"></transactionManager><!-- POOLED:mybatis自带的数据源，JNDI:基于tomcat的数据源 --><dataSource type="POOLED"><property name="driver" value="${driver}"/><property name="url" value="${url}"/><property name="username" value="${username}"/><property name="password" value="${password}"/></dataSource></environment></environments><!-- 将mapper文件加入到配置文件中 将来mapper文件很多所以是mappers --><mappers><mapper resource="cn/bdqn/dao/UserMapper.xml"/><mapper resource="cn/bdqn/dao/RoleMapper.xml"/></mappers> </configuration>
测试
//查询 @Testpublic void getUserListTest(){SqlSession sqlSession = null;try {List<User> userList = new ArrayList<User>();sqlSession = MyBatisUtil.createSqlSession();userList = sqlSession.selectList("cn.bdqn.dao.UserMapper.getUserList");for(User user:userList){logger.debug("user的id==="+user.getId());}} catch (Exception e) {// TODO: handle exception e.printStackTrace();sqlSession.rollback();}finally{MyBatisUtil.closeSqlSession(sqlSession);}}
