mybatis-plus的QueryWrapper

mybatis-plus的QueryWrapper

基本条件查询

QueryWrapper<Student> wapper=new QueryWrapper();
//条件值等于
//		wapper.eq("stuName","溪风");
//条件不等于空的
//		wapper.isNotNull("create_time");
//条件值大于指定值
//		wapper.gt("stuAge",19);
//模糊查询
wapper.like("stuId","9");
//排序倒序
wapper.orderByDesc("stuAge");
List<Student> students = studentMapper.selectList(wapper);
students.forEach(System.out::println);

查询指定字段

方式1

QueryWrapper<Student> wapper=new QueryWrapper();
//以下两个效果一样
//wapper.select("stuId,stuName,create_time");
wapper.select("stuId","stuName","create_time");
List<Student> students = studentMapper.selectList(wapper);
students.forEach(System.out::println);

方式2

QueryWrapper<Student> wapper=new QueryWrapper();
//传入实体的Class，然后通过反射获取实体的相关信息，可根据属性名、字段名，表达式一系列操作进行过滤
//以下为简单操作，更多的使用方法请看源码类TableFieldInfo
wapper.select(Student.class,on -> {
    if(on.getField().getName().equals("stuId")||
       on.getField().getName().equals("stuName")){
        return true;
    }
    return false;
});
List<Student> students = studentMapper.selectList(wapper);
students.forEach(System.out::println);

更多参考官网

https://baomidou.com/guide/wrapper.html#select