MyBtis动态sql及多表查询
作者：互联网
MyBatis映射文件深入
返回主键
userGeneratedKeys
向数据库保存一个user对象后，然后在控制台记录下此新增的user的主键值（id）
userGeneratedKeys属性，此方式支持主键自增1.接口方法
/**
* 向数据库保存一个user对象后, 然后在控制台记录下此新增user的主键值(id)
* useGeneratedKeys属性 此方式只支持主键自增
* @param user
*/
public void addUser(User user);
2.mapper.xml配置文件
<insert id="addUser" parameterType="User" useGeneratedKeys="true" keyColumn="id" keyProperty="id">
insert into user(username,birthday,sex,address)values
(#{username},#{birthday},#{sex},#{address})
</insert>
3.测试代码
@Test
public void addUser(){
//获取sqlSession会话
SqlSession sqlSession = MybatisUtil.openSession();
//通过代理加载接口中的方法
GetGenerateKeysUserMapper mapper = sqlSession.getMapper(GetGenerateKeysUserMapper.class);
//创建对象
User user = new User();
user.setUsername("小明");
user.setBirthday(new Date());
user.setSex("男");
user.setAddress("上海");
//执行方法
mapper.addUser(user);
//提交事务，释放资源
MybatisUtil.commit(sqlSession);
MybatisUtil.close(sqlSession);
//获取id
System.out.println(user.getId());
}
selectKey
相关属性
keyColumn 表示主键列
keyProperty实体主键属性
resultType实体主键属性类型
order 表示此标签内SQL语句在insert之前执行还是之后执行
after:之后执行
before：之前执行
LAST_INSERT_ID()函数主要用于获取最后一次插入数据时的id
1.接口方法
/**
* 向数据库保存一个user对象后, 然后在控制台记录下此新增user的主键值(id)
* LAST_INSERT_ID()函数 该函数是mysql提供的一个高级查询的函数，主要用于获取最后一次插入数据时的id
* @param user
*/
void addUser1(User user);
2.mapper.xml配置文件
<insert id="addUser1" parameterType="User">
<selectKey keyColumn="id" keyProperty="id" resultType="int" order="AFTER">
SELECT LAST_INSERT_ID()
</selectKey>
insert into user(username,birthday,sex,address)values
(#{username},#{birthday},#{sex},#{address})
</insert>
3.测试类
@Test
public void addUser1(){
SqlSession sqlSession = MybatisUtil.openSession();
GetGenerateKeysUserMapper mapper = sqlSession.getMapper(GetGenerateKeysUserMapper.class);
//创建对象
User user = new User();
user.setUsername("karyy");
user.setBirthday(new Date());
user.setSex("女");
user.setAddress("深圳");
mapper.addUser1(user);
MybatisUtil.commit(sqlSession);
MybatisUtil.close(sqlSession);
System.out.println(user.getId());
}
动态SQL
if标签
1. if 接口
/**
* 把id和username封装到user对象中，将user对象中不为空的属性作为查询条件
* @param user
* @return
*/
public List<User>findByAndUserNameIf(User user);
2. mapper.xml配置
<!--
if标签 条件判断
where标签 相当于 where 1=1 功能，如果没有条件情况下 where语句不在sql语句拼接
可以去掉第一个 and 或者 or
-->
<!--把id和username封装到user对象中，将user对象中不为空的属性作为查询条件-->
<select id="findByAndUserNameIf" parameterType="User" resultType="User">
select * from user
<where>
<if test="id != null">
and id = #{id}
</if>
<if test="username != null">
and username = #{username}
</if>
</where>
</select>
3. 测试类
@Test
public void findByAndUserNameIf(){
SqlSession sqlSession = MybatisUtil.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User user = new User();
user.setUsername("jack");
List<User> userList = mapper.findByAndUserNameIf(user);
for (User user1 : userList) {
System.out.println(user1);
}
MybatisUtil.commit(sqlSession);
MybatisUtil.close(sqlSession);
}
set标签
1. set接口
/**
* 动态更新user表数据，如果该属性有值就更新，没有值不做处理
* @param user
*/
public void updateUserSet(User user);
2. mapper.xml接口
<!--动态更新user表数据，如果该属性有值就更新，没有值不做处理-->
<select id="updateUserSet" parameterType="User">
update user
<set>
<if test="username != null">
username = #{username}
</if>
<if test="birthday != null">
birthday = #{birthday}
</if>
<if test="sex != null">
sex = #{sex}
</if>
<if test="address != null">
address = #{address}
</if>
</set>
where id = #{id}
</select>
3. 测试类
@Test
public void updateUserSet(){
SqlSession sqlSession = MybatisUtil.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User user = new User();
user.setId(53);
user.setUsername("java");
mapper.updateUserSet(user);
MybatisUtil.commit(sqlSession);
MybatisUtil.close(sqlSession);
}
forEachList标签
1. forEachList接口
/**
* 根据多个id查询，user对象的集合
* @param list
* @return
*/
public List<User>findUsersForEachList(List<Integer> list);
2. forEachList.xml配置文件
<!--
collection代表要遍历的集合元素
open代表语句的开始部分
close代表结束部分
item代表遍历集合的每个元素，生成的变量名
sperator代表分隔符
-->
<select id="findUsersForEachList" parameterType="list" resultType="User">
select * from user where id in
<foreach collection="list" open="(" close=")" item="id" separator=",">
#{id}
</foreach>
</select>
3. forEachList类
@Test
public void findUsersForEachList(){
SqlSession sqlSession = MybatisUtil.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
ArrayList<Integer> list = new ArrayList<>();
list.add(49);
list.add(50);
list.add(52);
List<User> userList = mapper.findUsersForEachList(list);
for (User user : userList) {
System.out.println(user);
}
MybatisUtil.close(sqlSession);
}
forEachArray标签
1. forEachArray接口
/**
* 普通数组
* @param ids
* @return
*/
public List<User>findUserForEachArray(Integer[] ids);
2. forEachArray.xml配置文件
<select id="findUserForEachArray" parameterType="int[]" resultType="User">
select * from user where id in
<foreach collection="array" open="(" close=")" item="id" separator=",">
#{id}
</foreach>
</select>
3. forEachArray测试类
@Test
public void findUserForEachArray(){
SqlSession sqlSession = MybatisUtil.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
ArrayList<Integer> list = new ArrayList<>();
list.add(49);
list.add(50);
list.add(52);
Integer[] ids = list.toArray(new Integer[list.size()]);
List<User> userList = mapper.findUserForEachArray(ids);
for (User user : userList) {
System.out.println(user);
}
MybatisUtil.close(sqlSession);
}
复杂查询
一对多查询
1. 接口实现
/**
* 根据用户的id查询订单(一对多)
* @param id
* @return
*/
public User findByIdWithOrder(Integer id);
2. xml配置
<!--一对多-->
<resultMap id="UserMap" type="User">
<id column="id" property="id"></id>
<result column="username" property="username"></result>
<result column="birthday" property="birthday"></result>
<result column="sex" property="sex"></result>
<!--
property="orderList" 关联实体集合的属性名
ofType="com.itfxp.domain.Order" 关联实体的java类型（集合泛型的类型）
-->
<collection property="order" ofType="Order">
<id column="oid" property="id"></id>
<result column="ordertime" property="ordertime"></result>
<result column="money" property="money"></result>
</collection>
</resultMap>
<select id="findByIdWithOrder" parameterType="int" resultMap="UserMap">
select *,o.id oid from user u,orders o
where u.id = o.uid and u.id = #{id}
</select>
3. 测试**
/**
* 一对多
*/
@Test
public void findByIdWithOrder(){
SqlSession sqlSession = MybatisUtil.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User byIdWithOrder = mapper.findByIdWithOrder(41);
System.out.println(byIdWithOrder);
MybatisUtil.close(sqlSession);
}
一对一查询
1. 接口实现
/**
* 根据Order id查询用户
* @param id
* @return
*/
public Order findByIdWithUser(int id);
2. xml配置
<resultMap id="OrderMap" type="Order">
<id column="id" property="id"></id>
<result column="ordertime" property="ordertime"></result>
<result column="money" property="money"></result>
<!--
property关联实体的属性名
javaType关联实体java类型
-->
<association property="user" javaType="User">
<id column="uid" property="id"></id>
<result column="username" property="username"></result>
<result column="birthday" property="birthday"></result>
<result column="sex" property="sex"></result>
<result column="address" property="address"></result>
</association>
</resultMap>
<select id="findByIdWithUser" parameterType="int" resultMap="OrderMap">
select * from orders o,user u
where o.uid = u.id and o.id = #{id}
</select>
3. 测试
/**
* 根据Order id查询用户
* @return
*/
@Test
public void findByIdWithUser(){
SqlSession sqlSession = MybatisUtil.openSession();
OrderMapper mapper = sqlSession.getMapper(OrderMapper.class);
Order byIdWithUser = mapper.findByIdWithUser(1);
System.out.println(byIdWithUser);
}
多对多查询
1. 接口实现
public User findByIdWithRole(Integer id);
2. xml配置
<!--多对多-->
<resultMap id="userAndRoleMap" type="User">
<id column="id" property="id"></id>
<result column="username" property="username"></result>
<result column="birthday" property="birthday"></result>
<result column="sex" property="sex"></result>
<result column="address" property="address"></result>
<collection property="roleList" ofType="Role">
<id column="rid" property="id"></id>
<result column="role_name" property="roleName"></result>
<result column="role_desc" property="roleDesc"></result>
</collection>
</resultMap>
<select id="findByIdWithRole" parameterType="int" resultMap="userAndRoleMap">
select * from user u,role r,user_role ur
where u.id = ur.uid and r.id = ur.rid and u.id = #{id}
</select>
3. 测试
/**
* 多对多
*/
@Test
public void findByIdWithRole(){
SqlSession sqlSession = MybatisUtil.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User user = mapper.findByIdWithRole(41);
System.out.println(user);
MybatisUtil.close(sqlSession);
}
标签：MybatisUtil,mapper,MyBtis,及多表,sqlSession,user,sql,id,User 来源： https://blog.csdn.net/qq_41934990/article/details/118394005