MyBatisPlus之AbstractWrapper

说明:

QueryWrapper(LambdaQueryWrapper) 和 UpdateWrapper(LambdaUpdateWrapper) 的父类
用于生成 sql 的 where 条件, entity 属性也用于生成 sql 的 where 条件
注意: entity 生成的 where 条件与使用各个 api 生成的 where 条件没有任何关联行为

allEq(Map<R, V> params)
allEq(Map<R, V> params, boolean null2IsNull)
allEq(boolean condition, Map<R, V> params, boolean null2IsNull)

个别参数说明:

params : key为数据库字段名,value为字段值
null2IsNull : 为true则在map的value为null时调用 isNull 方法,为false时则忽略value为null的

例1: allEq({id:1,name:"老王",age:null})--->id = 1 and name = '老王' and age is null
例2: allEq({id:1,name:"老王",age:null}, false)--->id = 1 and name = '老王'

allEq(BiPredicate<R, V> filter, Map<R, V> params)
allEq(BiPredicate<R, V> filter, Map<R, V> params, boolean null2IsNull)
allEq(boolean condition, BiPredicate<R, V> filter, Map<R, V> params, boolean null2IsNull)

个别参数说明:

filter : 过滤函数,是否允许字段传入比对条件中
params 与 null2IsNull : 同上

例1: allEq((k,v) -> k.indexOf("a") >= 0, {id:1,name:"老王",age:null})--->name = '老王' and age is null
例2: allEq((k,v) -> k.indexOf("a") >= 0, {id:1,name:"老王",age:null}, false)--->name = '老王'

eq(R column, Object val)
eq(boolean condition, R column, Object val)

eq("name", "老王")--->name = '老王'

ne(R column, Object val)
ne(boolean condition, R column, Object val)

例: ne("name", "老王")--->name <> '老王'

gt(R column, Object val)
gt(boolean condition, R column, Object val)

例: gt("age", 18)--->age > 18

ge(R column, Object val)
ge(boolean condition, R column, Object val)

例: ge("age", 18)--->age >= 18

lt(R column, Object val)
lt(boolean condition, R column, Object val)

例: lt("age", 18)--->age < 18

le(R column, Object val)
le(boolean condition, R column, Object val)

例: le("age", 18)--->age <= 18

/**
 * 带条件的分页查询
 * @param current
 * @param limit
 * @param teacherQuery
 * @return
 */
@Override
public Page<EduTeacher> pageListTeacherCondition(long current, Long limit, TeacherQuery teacherQuery){

    //创建Page对象
    Page<EduTeacher> eduTeacherPage = new Page<>(current,limit);

    //构建条件
    QueryWrapper<EduTeacher> wrapper = new QueryWrapper<>();

    //获取传入讲师的条件是否为空
    //讲师名
    String name = teacherQuery.getName();
    //讲师级别
    Integer level = teacherQuery.getLevel();
    //开始时间
    String gmtCreate = teacherQuery.getGmtCreate();
    //结束时间
    String gmtModified = teacherQuery.getGmtModified();

    //多条件组合查询
    //判断条件值是否为空,如果不为空拼接条件
    if (!StringUtils.isEmpty(name)){
        //构建条件 模糊查询
        wrapper.like("name",name);
    }

    if (!StringUtils.isEmpty(level)){
        //等于
        wrapper.eq("level",level);
    }

    if (!StringUtils.isEmpty(gmtCreate)){
        //大于等于
        wrapper.ge("gmt_create",gmtCreate);
    }

    if (!StringUtils.isEmpty(gmtModified)){
        //小于等于
        wrapper.le("gmt_modified",gmtModified);
    }

    //调用mybatis plus分页方法进行查询
    eduTeacherMapper.selectPage(eduTeacherPage,wrapper);

    //通过Page对象获取分页信息
    //long current = page.getCurrent();//当前页
    List<EduTeacher> records = eduTeacherPage.getRecords(); //每页的数据 list集合
    //long size = eduTeacherPage.getSize(); //每页显示的条数
    long total = eduTeacherPage.getTotal(); //总记录数
    long pages = eduTeacherPage.getPages(); //总页数

    boolean pagehasNext = eduTeacherPage.hasNext(); //下一页
    boolean pagehasPrevious = eduTeacherPage.hasPrevious(); //上一页
    
    return eduTeacherPage;
}

select * from user where id in [ 1,2,3] and (user_name like '%'+userName+'%' or address like '%'+address+'%';

EntityWrapper<userEntity> entityEntityWrapper = new EntityWrapper<>();
//在这里我们使用MP的selectPage方法去查，关于MP搭建可以去看之前的博文（关于mybatis-plus的）
 
Page<userEntity> userList= qdDeviceService.selectPage(new Page<userEntity>(),
//先来构建in的条件
                entityEntityWrapper.in("device_id",ids)
//之后以and连接并列的条件 后面更1=1 来保持成立的确定性
                        .and("1=1")
//之后再以like来拼接你所需要的模糊查询
                        .like("user_name", (String) params.get("userName"))
                        .like("address", (String) params.get("address"))
        );
//以上就是EntityWrapper的方式去查询

QueryWrapper<userEntity> userWrapper = new QueryWrapper<>();
String userName= (String) map.get("userName");
String address= (String) map.get("address");
 
 
userWrapper.and(wrapper -> wrapper.like("user_name", userName).or().like("address", address);

 LambdaQueryWrapper<Article> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.eq(Article::getCatId,10);
        queryWrapper.and(x->x.like(Article::getKeywords,keywords).or().like(Article::getTitle,keywords));
        queryWrapper.select(Article::getAuthor,Article::getCode,Article::getChildTitle,Article::getTitle);
        List<Article> articles = articleMapper.selectList(queryWrapper);
        articles.forEach(x-> System.out.println("文章关键字：" + x.getKeywords() + ",文章标题：" + x.getTitle()));