Mybatis 级联查询collection中javaType遇到别名不存在的问题

实体类

User

private Integer id; // 主键
    private Date birthday; // 生日
    private String gender; // 性别
    private String username; // 用户名，唯一
    private String password; // 密码
    private String remark; // 备注
    private String station; // 状态
    private String telephone; // 联系电话
    private Set<Role> roles = new HashSet<Role>(0);//对应角色集合

Role

private Integer id;
    private String name; // 角色名称
    private String keyword; // 角色关键字，用于权限控制
    private String description; // 描述
    private Set<User> users = new HashSet<User>(0);
    private Set<Permission> permissions = new HashSet<Permission>(0);
    private LinkedHashSet<Menu> menus = new LinkedHashSet<Menu>(0);

Permission

 private Integer id;
    private String name; // 权限名称
    private String keyword; // 权限关键字，用于权限控制
    private String description; // 描述
    private Set<Role> roles = new HashSet<Role>(0);

mapper.xml文件

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" >
<mapper namespace="com.gzy.dao.UserDao">

    <resultMap id="baseUserResultMap" type="com.gzy.health.pojo.User">
        <id column="id" property="id"/>
    </resultMap>

    <resultMap id="userResultMap" type="com.gzy.health.pojo.User" extends="baseUserResultMap">
        <collection property="roles" javaType="set" ofType="com.gzy.health.pojo.Role"
        column="user_id=id" select="com.gzy.dao.RoleDao.getRoleByUserId"></collection>
    </resultMap>

    <select id="getUserByName" resultMap="userResultMap">
     select * from t_user where username=#{username}
    </select>
</mapper>

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="com.gzy.dao.RoleDao">
    <resultMap id="baseRoleResultMap" type="com.gzy.health.pojo.Role">
        <id property="id" column="id"/>
     </resultMap>
    <resultMap id="roleResultMap" type="com.gzy.health.pojo.Role" extends="baseRoleResultMap">
        <collection property="permissions" javaType="set"
                    ofType="com.gzy.health.pojo.Permission" column="role_id=id" select="com.gzy.dao.PermissionDao.getPermissionByRoleId"/>
    </resultMap>
    <select id="getRoleByUserId" resultMap="roleResultMap">
        SELECT * FROM t_role WHERE id IN(SELECT role_id FROM t_user_role WHERE user_id=#{user_id})
    </select>
</mapper>

PermissionMapper.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.gzy.dao.PermissionDao">
    <select id="getPermissionByRoleId" resultType="Permission">
       SELECT * FROM t_permission WHERE id IN(SELECT permission_id
       FROM t_role_permission  WHERE role_id=#{role_id})
    </select>
</mapper>

我在开发遇到的问题是<collection >中的 javaTypee属性没有对应SET集合类型对应的别名，然后翻底层发现，mybatis根本没有提供SET集合的别名。所以需要自己注册别名。

注册很简单只要在mybatis配置文件中添加：

<typeAliases>
        <typeAlias alias="set" type="java.util.Set"/>
    </typeAliases>

这样就可以解决问题了。

最后编辑于：2019.07.27 11:08:05