LambdaQueryWrapper、MybatisPlus提供的基本接口方法、增删改查常用的接口方法、自定义 SQL

DAY26.2 Java核心基础

MybatisPlus提供的基本接口方法

分页查询

导入依赖springboot整合Mybatis-plus

<dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-boot-starter</artifactId><version>3.4.3</version>
</dependency>

创建Page对象，通过usermapper里面的selectPage查询

@Test
public void test4(){Page<User> userPage = userMapper.selectPage(new Page<>(0, 10), null);System.out.println(userPage.getRecords());System.out.println(userPage.getCurrent());System.out.println(userPage.getPages());System.out.println(userPage.getSize());
}

测试输出：

可以看见它并没有分页查询，而是把表中所有的数据查询出来了

为什么呢？

因为我们没有配置分页配置类

MybatisPlusConfig配置分页

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;@Configuration
public class MybatisPlusConfig {@Beanpublic MybatisPlusInterceptor mybatisPlusInterceptor() {MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();// 添加分页插件interceptor.addInnerInterceptor(new PaginationInnerInterceptor());return interceptor;}
}

我们再次查询

可以看见实现了分页查询，只查询了10个数据

增删改查常用的接口方法

查询

@Test
public void test6(){// 查询所有LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();queryWrapper.eq(User::getId,  1);List<User> users1 = userMapper.selectList(queryWrapper);System.out.println(users1);// 批量查询List<User> users2 = userMapper.selectBatchIds(Arrays.asList(1, 2, 3));System.out.println(users2);// 查询数量System.out.println(userMapper.selectCount(null));HashMap<String, Object> stringObjectHashMap = new HashMap<>();stringObjectHashMap.put("id", 1);System.out.println(userMapper.selectByMap(stringObjectHashMap));// 查询单个数据User user = userMapper.selectOne(queryWrapper);
}

增加

@Test
public void test7(){User user = new User();user.setName("张三");user.setRole("admin");user.setAge(18);user.setEmail("[e-mail]");user.setPwd("123456");int insert = userMapper.insert(user);System.out.println(insert);
}

更新

@Test
public void test8() {//修改User user = new User();user.setId(1);user.setName("张三");user.setRole("admin");user.setAge(18);user.setEmail("[e-mail]");user.setPwd("123456");// 根据id更新int update = userMapper.updateById(user);System.out.println(update);// 根据条件更新(wrapper)LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();queryWrapper.eq(User::getName, "张三");System.out.println(userMapper.update(user, queryWrapper));
}

删除

@Test
public void test9() {// 根据id删除int delete = userMapper.deleteById(1);System.out.println(delete);// 根据条件删除(wrapper)LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();queryWrapper.eq(User::getName, "张三");int delete1 = userMapper.delete(queryWrapper);// 批量删除userMapper.deleteBatchIds(Arrays.asList(1, 2, 3));// 根据map键值对删除HashMap<String, Object> stringObjectHashMap = new HashMap<>();stringObjectHashMap.put("id", 1);stringObjectHashMap.put("name", "张三");userMapper.deleteByMap(stringObjectHashMap);
}

自定义 SQL

UserMapper

public interface UserMapper extends BaseMapper<User> {@Select("select * from user where name = #{name}")User queryByName(String name);
}

@Test
public void test10() {User user = userMapper.queryByName("张三");System.out.println(user);
}