MP实现常规增删改操作 - 《Java就业班复习》

MP实现分页查询
MP封装Service
- 编写MyMetaObjectHandler

插入记录代码

package com.itheima.test;

import com.itheima.dao.UserMapper;
import com.itheima.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
public class TestMybatisPlus02 {

@Autowired<br />    private UserMapper userMapper;
/**<br />     * 添加:<br />     *      在添加数据信息时,如果没有提供id的值,则id由MybatisPlus自动维护<br />     *      添加成功后,会自动将新增的数据的id回填到当前对象中.<br />     */<br />    @Test<br />    public void testInsert(){<br />        //User user = new User();<br />        //user.setUserName("damimi");<br />        //user.setAge(18);<br />        //user.setName("大幂幂");<br />        //user.setPassword("666");<br />        //user.setEmail("damimi@qq.com");<br />        // 使用java的构建者模式,帮我们创建对象<br />        User user = User.builder()<br />                .userName("liuyan")<br />                .age(38)<br />                .name("柳岩")<br />                .email("liuyan@itcast.cn")<br />                .password("123")<br />                .build();<br />        int i = userMapper.insert(user);<br />        if (i>0) {<br />            System.out.println("添加成功");<br />        }<br />        System.out.println(user);<br />    }<br />}

主键生成策略:
是指为数据库生成主键的方式，我们前面学的数据库主键自增也是一种生成主键的策略，当然除了数据库服务端帮助我们维护主键之外，客户端也可以对主键值进行生成维护。

MP主键生成策略示例：
package com.itheima.pojo;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
// @TableName: 指定当前对象对应的数据库表
@TableName(“tb_user”)
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class User {

/**<br />     * @TableId: 指定当前表的主键<br />     *      value: 建立数据库主键字段与实体字段的对应关系<br />     *      type: 设置主键生成策略,<br />     *          默认情况下使用雪花算法<br />     *          IdType.AUTO:使用数据库的主键自增<br />     */<br />    @TableId(type = IdType.AUTO)<br />    private Long id;<br />    private String userName;<br />    private String password;<br />    private String name;<br />    private Integer age;<br />    private String email;<br />}

package com.itheima.pojo;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
// @TableName: 指定当前对象对应的数据库表
@TableName(“tb_user”)
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class User {

/**<br />     * @TableId: 指定当前表的主键<br />     *      value: 建立数据库主键字段与实体字段的对应关系<br />     *      type: 设置主键生成策略,<br />     *          IdType.NONE/ASSIGN_ID:默认情况下使用雪花算法<br />     *          IdType.AUTO:使用数据库的主键自增<br />     *          ASSIGN_UUID:使用UUID生成一个全局唯一字符串<br />     */<br />    @TableId(type = IdType.AUTO)<br />    private Long id;<br />    private String userName;<br />    private String password;<br />    // 建立数据库字段与实体字段的对应关系 @TableField("与数据库字段名对应")<br />    @TableField("t_name")<br />    private String name;<br />    private Integer age;<br />    // 忽略此字段<br />    @TableField(exist = false)<br />    private String email;<br />}

@Test
public void test04(){
// 创建用户对象
User user = User.builder()
//.id(666L) // 当设置id时,则使用设置的值
.userName(“damimi”)
.name(“大幂幂999”)
.age(18)
.email(“damimi@qq.com”)
.password(“666”)
.build();
int i = userMapper.insert(user);
if (i>0){
System.out.println(“添加成功…”);
}
}

/
根据id删除
/
@Test
public void testDelete1(){
int i = userMapper.deleteById(1448842113843228674L);
if (i>0) {
System.out.println(“删除成功”);
}
}
/
批量删除
/
@Test
public void testDelete2(){
ArrayList list = new ArrayList<>();
list.add(1448841494474530818L);
list.add(1448839707025780737L);
int i = userMapper.deleteBatchIds(list);
if (i>0) {
System.out.println(“删除成功”);
}
}

/**<br />     * 根据条件删除<br />     */<br />    @Test<br />    public void testDelete3(){<br />        // 将删除的条件设置到map集合中<br />        Map<String, Object> map = new HashMap<>();<br />        // map的键为数据库字段名<br />        //map.put("id",1448832902639939586L);<br />        map.put("user_name","damimi");<br />        int i = userMapper.deleteByMap(map);<br />        if (i>0) {<br />            System.out.println("删除成功");<br />        }<br />    }

/*
修改用户信息
*/
@Test
public void testUpdate(){
// 构建修改后的数据信息
User user = User.builder()
.id(2L)
.userName(“liuyan”)
.password(“6669”)
.name(“柳岩”)
.age(18)
.email(“liuyan@qq.com”)
.build();
int i = userMapper.updateById(user);
System.out.println(i>0?”修改成功”:”修改失败”);
}

MP实现分页查询

1.配置分页拦截器
package com.itheima.config;
import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/*
@Description:
@Version: V1.0
/
@Configuration
public class MybatisPlusConfig {
@Bean
public MybatisPlusInterceptor mybatisPlusInterceptor() {
MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
PaginationInnerInterceptor paginationInterceptor = new PaginationInnerInterceptor(DbType.MYSQL);
// 设置请求的页面大于最大页后操作， true调回到首页，false 继续请求默认false
// paginationInterceptor.setOverflow(false);
// 设置最大单页限制数量，-1不受限制
paginationInterceptor.setMaxLimit(-1L);
interceptor.addInnerInterceptor(paginationInterceptor);
return interceptor;
}
}

查询测试
package com.itheima;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.itheima.mapper.UserMapper;
import com.itheima.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
public class UserMapperQueryTest {

@Autowired<br />    private UserMapper userMapper;
/**<br />     * 分页查询<br />     */<br />    @Test<br />    public void testPage(){<br />        // 创建分页对象<br />        IPage<User> page = new Page<>(2, 3);<br />        IPage<User> userPage = userMapper.selectPage(page, null);<br />        System.out.println(page==userPage);
    // 获取分页数据信息<br />        List<User> userList = page.getRecords();<br />        for (User user : userList) {<br />            System.out.println(user);<br />        }<br />        // 当前页<br />        long current = page.getCurrent();<br />        // 每页显示条数<br />        long size = page.getSize();<br />        // 总条数<br />        long total = page.getTotal();<br />        // 总页数<br />        long pages = page.getPages();<br />        System.out.println(current);<br />        System.out.println(size);<br />        System.out.println(total);<br />        System.out.println(pages);<br />    }<br />}

查询测试
/*
查询用户中姓名包含”伤”，密码为”123456”,且年龄为19或者25或者29，查询结果按照年龄降序排序；
*/
@Test
public void testFind1(){
QueryWrapper wrapper = new QueryWrapper<>();
wrapper.like(“user_name”,”伤”)
.eq(“password”,”123456”)
.in(“age”,19,25,29)
.orderByDesc(“age”);
// 查询所有
//List list = userMapper.selectList(null);
List list = userMapper.selectList(wrapper);
for (User user : list) {
System.out.println(user);
}
}

/*
查询用户名为”liuyan”或者年龄大于23的用户信息；
*/
@Test
public void testFind2(){
QueryWrapper wrapper = new QueryWrapper<>();
wrapper.eq(“user_name”,”liuyan”)
.or()
.gt(“age”,23);
// 查询所有
//List list = userMapper.selectList(null);
List list = userMapper.selectList(wrapper);
for (User user : list) {
System.out.println(user);
}
}

/*
模糊查询
*/
@Test
public void testFind3(){
QueryWrapper wrapper = new QueryWrapper<>();
wrapper.like(“user_name”,”伤”);
// 查询所有
//List list = userMapper.selectList(null);
List list = userMapper.selectList(wrapper);
for (User user : list) {
System.out.println(user);
}
}

测试代码
/*
排序查询
*/
@Test
public void testFind4(){
QueryWrapper wrapper = new QueryWrapper<>();
wrapper.orderByAsc(“age”).orderByDesc(“id”);
// 查询所有
//List list = userMapper.selectList(null);
List list = userMapper.selectList(wrapper);
for (User user : list) {
System.out.println(user);
}
}

/*
指定查询字段
*/
@Test
public void testFind5(){
QueryWrapper wrapper = new QueryWrapper<>();
wrapper.orderByAsc(“age”).orderByDesc(“id”).select(“id”,”user_name”,”age”);
// 查询所有
//List list = userMapper.selectList(null);
List list = userMapper.selectList(wrapper);
for (User user : list) {
System.out.println(user);
}
}

/*
分页查询
*/
@Test
public void testFind6(){
// 创建分页对象
IPage page = new Page<>(1, 3);
// 拼接分页条件
QueryWrapper wrapper = new QueryWrapper<>();
wrapper.like(“user_name”,”伤”);
userMapper.selectPage(page, wrapper);

    // 获取分页数据信息<br />        List<User> userList = page.getRecords();<br />        for (User user : userList) {<br />            System.out.println(user);<br />        }<br />        // 当前页<br />        long current = page.getCurrent();<br />        // 每页显示条数<br />        long size = page.getSize();<br />        // 总条数<br />        long total = page.getTotal();<br />        // 总页数<br />        long pages = page.getPages();<br />        System.out.println(current);<br />        System.out.println(size);<br />        System.out.println(total);<br />        System.out.println(pages);<br />    }

@Test
public void testFind7(){
// 存在硬编码问题,扩展维护成本高
/QueryWrapper wrapper = new QueryWrapper<>();
wrapper.like(“user_name”,”伤”)
.eq(“password”,”123456”)
.in(“age”,19,25,29)
.orderByDesc(“age”);/
// 创建LambdaQueryWrapper对象
// User::getUserName: 动态读取实体中成员属性的名称.
//LambdaQueryWrapper wrapper = new LambdaQueryWrapper<>();
LambdaQueryWrapper wrapper = Wrappers.lambdaQuery();
wrapper.like(User::getUserName,”伤”)
.eq(User::getPassword,”123456”)
.in(User::getAge,19,25,29)
.orderByDesc(User::getAge);
// 查询所有
//List list = userMapper.selectList(null);
List list = userMapper.selectList(wrapper);
for (User user : list) {
System.out.println(user);
}
}

/*
根据条件删除
*/
@Test
public void deleteTest1(){
LambdaUpdateWrapper wrapper = Wrappers.lambdaUpdate();
wrapper.eq(User::getId,1437238496724000769L);
int i = userMapper.delete(wrapper);
System.out.println(i);
}

/*
根据条件删除
*/
@Test
public void updateTest2(){
User user = User.builder()
.userName(“liuyan”)
.password(“6669”)
.name(“柳岩”)
.age(18)
.email(“liuyan@qq.com”).address(“上海”)
.build();
// 封装修改条件
LambdaUpdateWrapper wrapper = Wrappers.lambdaUpdate();
wrapper.eq(User::getId,1437234959319408644L)
.eq(User::getAge,18);
int i = userMapper.update(user, wrapper);
System.out.println(i);
}

MP封装Service

package com.itheima;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.conditions.update.LambdaUpdateWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.core.toolkit.Wrappers;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.itheima.mapper.UserMapper;
import com.itheima.pojo.User;
import com.itheima.service.UserService;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.omg.PortableInterceptor.USER_EXCEPTION;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;

/*
@Description
@Created by itheima
/
@SpringBootTest
public class MpTestService {
@Autowired
private UserService userService;

/**<br />     * @Description 测试查询操作 根据id查询<br />     */<br />    @Test<br />    public void test1(){<br />        User user = userService.getById(3l);<br />        System.out.println(user);<br />    }
/**<br />     * @Description 测试条件查询，且仅返回一个<br />     * getOne:sql查询的结果必须为1条或者没有，否则报错 ！！！！<br />     */<br />    @Test<br />    public void test2(){<br />        LambdaQueryWrapper<User> wrapper = Wrappers.lambdaQuery(User.class);<br />        wrapper.gt(User::getAge,20);<br />        User one = userService.getOne(wrapper);<br />        System.out.println(one);<br />    }
/**<br />     * @Description 根据条件批量查询<br />     */<br />    @Test<br />    public void test3(){<br />        LambdaQueryWrapper<User> wrapper = Wrappers.lambdaQuery(User.class);<br />        wrapper.gt(User::getAge,20);<br />        List<User> list = userService.list(wrapper);<br />        System.out.println(list);<br />    }
/**<br />     * @Description 根据条件批量查询并分页<br />     */<br />    @Test<br />    public void test4(){<br />        LambdaQueryWrapper<User> wrapper = Wrappers.lambdaQuery(User.class);<br />        wrapper.gt(User::getAge,20);<br />        //构建分页对象<br />        IPage<User> page=new Page<>(2,3);<br />        userService.page(page,wrapper);<br />        System.out.println(page.getRecords());<br />        System.out.println(page.getPages());<br />        System.out.println(page.getTotal());<br />    }
/**<br />     * @Description 测试服务层save保存单条操作<br />     */<br />    @Test<br />    public void test5(){<br />        User user1 = User.builder().name("wangwu").userName("laowang4").<br />                email("444@163.com").age(20).password("333").build();<br />        boolean isSuccess = userService.save(user1);<br />        System.out.println(isSuccess?"保存成功":"保存失败");<br />    }
/**<br />     * @Description 测试服务层批量保存<br />     */<br />    @Test<br />    public void test6(){<br />        User user2 = User.builder().name("wangwu2").userName("laowang2").<br />                email("444@163.com").age(20).password("333").build();<br />        User user3 = User.builder().name("wangwu3").userName("laowang3").<br />                email("444@163.com").age(20).password("333").build();<br />        boolean isSuccess = userService.saveBatch(Arrays.asList(user2, user3));<br />        System.out.println(isSuccess?"保存成功":"保存失败");<br />    }<br />    <br />    /**<br />     * @Description 根据id删除操作<br />     */<br />    @Test<br />    public void test7(){<br />        boolean isSuccess = userService.removeById(17l);<br />        System.out.println(isSuccess?"保存成功":"保存失败");<br />    }
/**<br />     * @Description 根据条件批量删除<br />     */<br />    @Test<br />    public void test8(){<br />        LambdaQueryWrapper<User> wrapper = Wrappers.lambdaQuery(User.class);<br />        wrapper.gt(User::getId,12)<br />                .gt(User::getAge,20);<br />        boolean remove = userService.remove(wrapper);<br />        System.out.println(remove);<br />    }
/**<br />     * @Description 测试根据id更新数据<br />     */<br />    @Test<br />    public void test9(){<br />        //UPDATE tb_user SET password=?, t_name=? WHERE id=?<br />        User user2 = User.builder().name("wangwu2").password("333").id(3l).build();<br />        boolean success = userService.updateById(user2);<br />        System.out.println(success);
}
/**<br />     * @Description 测试根据条件批量更新<br />     */<br />    @Test<br />    public void test10(){<br />        LambdaUpdateWrapper<User> wrapper = Wrappers.lambdaUpdate(User.class);<br />        //UPDATE tb_user SET age=? WHERE (id IN (?,?,?))<br />        wrapper.in(User::getId,Arrays.asList(1l,3l,5l)).set(User::getAge,40);<br />        boolean update = userService.update(wrapper);<br />        System.out.println(userService);
}<br />}<br />![image.png](https://cdn.nlark.com/yuque/0/2022/png/26700116/1656160706199-012897ee-f474-48a2-af8f-4f2a0744dcbb.png#clientId=uf82d1173-7ab8-4&crop=0&crop=0&crop=1&crop=1&from=paste&height=303&id=ue741138c&margin=%5Bobject%20Object%5D&name=image.png&originHeight=303&originWidth=767&originalType=binary&ratio=1&rotation=0&showTitle=false&size=36714&status=done&style=none&taskId=u2bec1c56-1d5a-44f0-a4ac-0f06187058e&title=&width=767)<br />![image.png](https://cdn.nlark.com/yuque/0/2022/png/26700116/1656160727449-fd46d72f-b2b6-439b-b7e7-5180cc78ead7.png#clientId=uf82d1173-7ab8-4&crop=0&crop=0&crop=1&crop=1&from=paste&height=482&id=u6203e50d&margin=%5Bobject%20Object%5D&name=image.png&originHeight=482&originWidth=287&originalType=binary&ratio=1&rotation=0&showTitle=false&size=15292&status=done&style=none&taskId=u7f263dfa-e58b-4db2-b329-7c2b2732a16&title=&width=287)

编写MyMetaObjectHandler

package cn.itcast.mp.handler;

import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import org.apache.ibatis.reflection.MetaObject;
import org.springframework.stereotype.Component;

@Component
public class MyMetaObjectHandler implements MetaObjectHandler {

@Override<br />    public void insertFill(MetaObject metaObject) {<br />        Object password = getFieldValByName("password", metaObject);<br />        if(null == password){<br />            //字段为空，可以进行填充<br />            setFieldValByName("password", "123456", metaObject);<br />        }<br />    }
@Override<br />    public void updateFill(MetaObject metaObject) {
}<br />}

测试
@Test
public void testQueryUesrById() {
User user1 = User.builder().age(18)
.email(“aa@itheima.com”)
.name(“小明”)
.password(“1234”)
.age(18)
.build();
userMapper.insert(user1);
}