MybatisPlus之QueryWrapper、LambdaQueryWrapper以及LambdaQueryChainWrapper用法 - donleo123 - 博客园

安宇雨 - 随手采集
2021-08-18 15:50:05
随手采集
0000-未整理-等待研究

MybatisPlus3.4.1版本自定义条件构造器

Wrapper之QueryWrapper、LambdaQueryWrapper以及LambdaQueryChainWrapper

1、QueryWrapper

.like("email", "24252") //email对应数据库中列名

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1 　　/**
2 * 条件构造器查询操作
3 */
4 @Test
5 void TestQueryWrapperSelect() { 6 //1、条件用法
7 List<User> userList = userMapper.selectList(new QueryWrapper<User>()
8 .like("email", "24252")
9 .between("age", 20, 22) 10 .or() 11 .eq("name", "zcx") 12 ); 13 System.out.println("userList:" + userList); 14
15 //2、排序用法
16 List<User> users = userMapper.selectList(new QueryWrapper<User>() 17 .eq("nick_name", "xx") 18 .orderByAsc("age") //升序 19 // .orderByDesc("age") //降序
20 .last("limit 0,3") //last用法：在sql末尾添加sql语句，有sql注入风险
21 ); 22 System.out.println("users:"+users); 23
24 }

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2、LambdaQueryWrapper

queryWrapper.eq(User::getName,"liangd1"); //可以通过Lambda获取数据库列名

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1 @Test
2 void TestLambdaQueryWrapper() { 3 //1、查询单条
4 LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
5 queryWrapper.eq(User::getName,"liangd1");
6 User selectOne = userMapper.selectOne(queryWrapper); 7 System.out.println(selectOne);
8
9 //2、查询list以及统计条数
10 queryWrapper.eq(User::getName, "zcx"); 11 List<User> userList = userMapper.selectList(queryWrapper); 12 System.out.println("userList:" + userList); 13 Integer result = userMapper.selectCount(queryWrapper); 14 System.out.println("result:" + result); 15 }

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3、LambdaQueryChainWrapper

1 //链式查询方式
2 User one = new LambdaQueryChainWrapper<>(userMapper) 3 .eq(User::getName, "liangd1") 4 .one();

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1 @Test
2 void TestLambdaQueryChainWrapper() { 3 //1、eq查询单条
4 User one = new LambdaQueryChainWrapper<>(userMapper)
5 .eq(User::getName, "liangd1")
6 .one();
7 System.out.println("UserOne:" + one); 8
9 //2、查询list
10 List<User> users = new LambdaQueryChainWrapper<>(userMapper) 11 .eq(User::getName, "zcx") 12 .list(); 13 System.out.println("UserList:" + users); 14
15 //3、模糊查询
16 List<User> LikeList = new LambdaQueryChainWrapper<>(userMapper) 17 .like(User::getEmail, "test") 18 .list(); 19 System.out.println("LikeUser:" + LikeList); 20 }

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创建于: 2021-08-18 15:50:04
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