MybatisPlus-条件构造器

Warpper 条件构造器定级接口

  我们在使用过程，就是去new QueryWarpper<T>()与new UpdateWarpper<T>()，完成相对复杂的sql拼接。

使用方式

1. 使用Mapper

Warpper接口的作用是提供一定逻辑去拼接sql语句。通过Dao层去执行sql语句。
代码实现：

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserMapper userMapper;

    private void queryAllUser() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByAsc("userId");
        List<User> list = userMapper.selectList(queryWrapper);
        list.forEach(System.out::println);
    }
}

2. 使用serviceImpl 实现类

MybatisPlus提供了对应的ServiceImpl辅助工具类，对业务逻辑进行部分封账，完成调用。

代码实现：

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {

    @Resource
    private UserStrMapper userStrMapper;

    private void queryAllUser() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByAsc("userId");
        // list 方法是serviceImpl 方法
        List<User> list = this.list(queryWrapper);
        list.forEach(System.out::println);
    }
}

QueryWrapper使用例

函数	说明	queryWrapper使用例子	对应sql
eq	等于(=)	queryWrapper.eq(“user_name”, “张三”);	user_name=“张三”
ne	不等于(<>)	queryWrapper.ne(“user_name”, “张三”);	user_name<>“张三”
gt	大于(>)	queryWrapper.gt(“level”, 1);	level>1
ge	大于等于(>=)	queryWrapper.ge(“level”, 1);	level>=1
lt	小于(<)	queryWrapper.lt(“level”, 1);	level<1
le	小于等于(<=)	queryWrapper.le(“level”, 1);	level<=1
between	值1和值2之间	queryWrapper.between(“level”, 1,10);	level>=1 and level <=10
notBetween	不在值1和值2之间	queryWrapper.notBetween(“level”, 1,10);	level<1 or level >10
like	模糊匹配 like %值%	queryWrapper.like(“user_name”, “张三”);	user_name like “%张三%”
not like	不模糊匹配 not like %值%	queryWrapper.notLike(“user_name”, “张三”);	user_name not like “%张三%”
likeLeft	左模糊匹配 like %值	queryWrapper.likeLeft(“user_name”, “张三”);	user_name like “%张三”
likeRight	右模糊匹配 like 值%	queryWrapper.likeRight(“user_name”, “张三”);	user_name like “张三%”
isNull	字段 为空	queryWrapper.isNull(“user_name”);	user_name is null
isNotNull	字段 不为空	queryWrapper.isNotNull(“user_name”);	user_name is not null
in	字段 in (v0，v1，…)	queryWrapper.in(“user_name”, {“张三”,“李四”,“王五”});	user_name in （“张三”,“李四”,“王五”）
notIn	字段 not in (v0，vl，…)	queryWrapper.notIn(“user_name”, {“张三”,“李四”,“王五”});	user_name not in （“张三”,“李四”,“王五”）
inSql	字段 in ( sql语句)	queryWrapper.in(“user_name”, (select name from student where age< 23));	user_name in (select name from student where age< 23)
notInSql	字段 not in ( sql语句)	queryWrapper.notIn(“user_name”, (select name from student where age< 23));	user_name not in (select name from student where age< 23)
groupBy	分组:GROUP BY 字段	queryWrapper.groupBy(“user_name”);	group by user_name
orderByAsc	排序:ORDER BY 字段 ASC	queryWrapper.orderByAsc(“createTime”);	order by createTime asc
orderByDesc	排序:ORDER BY 字段 DESC	queryWrapper.orderByDesc(“createTime”);	order by createTime desc
orderBy	排序:ORDER BY 字段	queryWrapper.orderBy(true, true, “createTime”);	order by createTime asc
or	拼接 OR。不调用or则默认为使用and连接	queryWrapper.eq(“id”, “1”).or().eq(“user_name”, “张三”);	id = 1 or name =‘张三’
and	拼接 AND	queryWrapper.eq(“id”, “1”).and(i->i.eq(“user_name”, “张三”));	id = 1 and name =‘张三’
apply	拼接 sql。说明: 该方法可用于数据库函数动态入参的params	queryWrapper.eq(“id”, user.getId()).apply(“date_format(‘createTime’,‘%Y-%m-%d’) = {0}”,“2023-07-25”);	date_format(‘createTime’,'%Y-%m-%d) =‘2023-07-25’")
last	无视优化规则直接拼接到 sql 的最后。 说明:只能调用一次,多次调用以最后一次为准 有sq1注入的风险,请谨慎使用	queryWrapper.last("" limit 1"");	limit 1
exists	拼接 EXISTS(sql语句)	queryWrapper.exists(“SELECT id FROM Student WHERE User.id = Student.userId”);	exists (“SELECT id FROM Student WHERE User.id = Student.userId”)
notExists	拼接 NOT EXISTS (sg1语句)	queryWrapper.notExists(“SELECT id FROM Student WHERE User.id = Student.userId”);	not exists (“SELECT id FROM Student WHERE User.id = Student.userId”)
nested	正常嵌套不带 AND或者 OR	queryWrapper.nested(i->i.eq(“id”,“1”).eq(“user_name”,“张三”));	id = 1 and user_name=“张三”
having	having ( sql语句)	queryWrapper.having(“sum(age) > {0}”,10);	having sum(age) > 10;

查询

查询用户，name不为空，name模糊查询，age大于值

	@Override
    public List<UserDto> queryByNameAndAge(String name, Integer age) {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.like("name", name)
        .gt("age", age)
        .isNull("name");
        List<User> users = this.list(queryWrapper); // mapper.selectList(queryWrapper)
        return userStrMapper.toDto(users);
    }

排序

查询用户，按name正序，按照age倒序

@Override
    public List<UserDto> query() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByAsc("name").orderByDesc("age");
        List<User> users = this.list(queryWrapper); // mapper.selectList(queryWrapper)
        return userStrMapper.toDto(users);
    }

删除

删除 年龄小于18 的用户

@Override
    public void deleteByAge() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.lt("age", "18");
        boolean i = this.remove(queryWrapper); // mapper.delete(queryWrapper)
    }

组合查询

查询 （name等于张三，并且年龄为18岁）or(name不为空）

    @Override
    public List<UserDto> queryByNameAndAge() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.and(item -> {
            item.like("name", "张三").eq("age", "18");
        }).or(item -> {
            item.isNull("name");
        });
        List<User> users = this.list(queryWrapper); // mapper.selectList(queryWrapper)
        return userStrMapper.toDto(users);
    }

字段查询

查询 name等于张三，并返回 姓名、年龄。并返回为 map

    @Override
    public List<Map<String,Object>> queryByNam() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.like("name", "张三").select("name","age");
		// 将数据与map以map方式返回
        List<Map<String,Object>> listMaps = this.listMaps(queryWrapper); // mapper.selectMap(queryWrapper);
        return userStrMapper.toDto(listMaps);
    }

子查询

    @Override
    public List<UserDto> childenQuery(String name) {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.inSql("name", "select name from sys_user where name is not null");
        List<User> users = this.list(queryWrapper); // mapper.selectList(queryWrapper)
        return userStrMapper.toDto(users);
    }

更新

更新 name等于张三的用户，其年龄改为25

    @Override
    public void updateUser() {
        UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();
        // set方法相当于 set，eq相当于 where
        updateWrapper.set("age", "25")
                .eq("name", "张三");
        this.update(updateWrapper); // mapper.update(queryWrapper)
    }

动态查询语句

    @Override
    public List<UserDto> query(String name,Integer age) {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        // 如果 true，则执行后面
        queryWrapper.like(StringUtils.isNotBlank(name),"name", name)
        // 如果年龄不为null且大于0，则执行 age>25
        .gt(age != null && age >0, "age", 25);
        List<User> users = this.list(queryWrapper);// mapper.selectList(queryWrapper)
        return userStrMapper.toDto(users);
    }

分页查询

    @Override
    public List<UserDto> query() {
        // 设置每页10条，查询第2页数据
        Page<User> pageConfig = new Page<>(2,10);
        Page<User> page = this.page(pageConfig); // mapper.selectPage(pageConfig,Wrappers.emptyWrapper())
        // 第2页的数据
        List<User> records = page.getRecords();
        // 总共多少条
        long total = page.getTotal();
        // 每页多少条
        long size = page.getSize();
        // 总共几页
        long pages = page.getPages();
        return userStrMapper.toDto(records);
    }

__EOF__

本文作者：之士咖啡
本文链接：https://www.cnblogs.com/zz-1q/p/17911690.html
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