sqlSession的获取

SqlSessionFactoryBean bean = new SqlSessionFactoryBean();bean.setDataSource(mysqlDataSource());bean.setConfigLocation(new PathMatchingResourcePatternResolver().getResource("classpath:mybatis/mybatis-config.xml"));bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/mysql/*.xml"));bean.setTypeAliasesPackage("com.getword.entity");sqlSessionFactory = bean.getObject();

one to one

方式一

假设user和role是一对一关系，中间表为Sys_user_role

public class SysUser{    private SysRole role;    ...}

    select    u.id,    u.userName userName,    u.userPassword userPassword,    r.id "role.id",    r.roleName "role.roleName"    from sys_user u    inner join sys_user_role ur on u.id=ur.userId    inner join sys_role r on r.id = ur.roleId    where u.id = #{id}

方式二

使用resultmap，和第一种方式类似

        
         
         
         
         
     
        select    u.id,    u.userName userName,    u.userPassword userPassword,    r.id roleId,    r.roleName roleName    from sys_user u    inner join sys_user_role ur on u.id=ur.userId    inner join sys_role r on r.id = ur.roleId    where u.id = #{id}

方式三，association一一对应

此种方式，对于多表查询，只会封装指定的result标签的字段

        
         
         
         
             
              
          
     
        select    u.id,    u.userName userName,    u.userPassword userPassword,    r.id roleId,    r.roleName roleName    from sys_user u    inner join sys_user_role ur on u.id=ur.userId    inner join sys_role r on r.id = ur.roleId    where u.id = #{id}

resultMap可以继承

        
         
             
              
          
     
        select    u.id,    u.userName userName,    u.userPassword userPassword,    r.id roleId,    r.roleName roleName    from sys_user u    inner join sys_user_role ur on u.id=ur.userId    inner join sys_role r on r.id = ur.roleId    where u.id = #{id}

方式四，association嵌套查询，最简单的方式

        
         
     
    
        
         
     
        select    u.id,    u.userName userName,    u.userPassword userPassword,    r.id roleId    from sys_user u    inner join sys_user_role ur on u.id=ur.userId    inner join sys_role r on r.id = ur.roleId    where u.id = #{id}

简写

        
         
     
        select    *    from sys_user u    inner join sys_user_role ur on u.id=ur.userId    where u.id = #{id}

one to many

方式一

        
         
         
     
    
        
             
              
          
     
        select    u.id,    u.userName userName,    u.userPassword userPassword,    r.id roleId,    r.roleName roleName    from sys_user u    inner join sys_user_role ur on u.id=ur.userId    inner join sys_role r on r.id = ur.roleId    where u.id = #{id}

对于id相同的user被归为一个user，相当于分组了