MyBatis-Plus中怎么使用EntityWrappe进行列表数据倒序设置

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使用EntityWrappe进行列表数据倒序设置

情景

项目中使用MyBatis-Plus的EntityWrapper，默认是升序，但实际项目中需要倒序显示，就查看了一下相关资料，在这里记录一下。

 EntityWrapper是个很强大的玩意，支持多条件查询 EntityWrapper() wrapper= new EntityWrapper(); wrapper.between(column, val1, val2) wrapper.groupBy(columns)  //对应sql中分组 wrapper.eq(column, params) //相当于where条件 wrapper.in(column, value) //sql中in wrapper.notIn(column, value) //sql中 not in wrapper.orderBy(columns, isAsc) //排序 wrapper.exists(value) //相对于sql中exists查询 wrapper.notExists(value) //相当于sql中not exists查询 wrapper.notBetween(column, val1, val2) //相当于sql中在某个范围内使用的between wrapper.ge(column, params) //大于等于 wrapper.le(column, params) //小于等于 wrapper.like(column, value) //模糊查询 wrapper.having(sqlHaving, params) //条件过滤

如下进行倒序案例

使用.orderBy("create_time",false)就可以实现倒序排列查询

 @Override    public PageUtils queryPage(Map params) {        //EntityWrapper 可以封装bean参数        String name=(String)params.get("name");        Page page = this.selectPage(                new Query(params).getPage(),                new EntityWrapper()                        .like(StringUtils.isNotBlank(name),"name", name)//根据公司名进行查询                        .orderBy("create_time",false)//按创建时间进行倒序查询        );         return new PageUtils(page);    }

根据上面的可以进行很多条件查询，有兴趣的可以自己试一试哦

条件构造器EntityWrapper用法

EntityWrapper 简介

1、 MybatisPlus 通过 EntityWrapper（简称 EW，MybatisPlus 封装的一个查询条件构造器）或者 Condition（与 EW 类似） 来让用户自由的构建查询条件，简单便捷，没有额外的负担， 能够有效提高开发效率。

2、实体包装器，主要用于处理 sql 拼接，排序，实体参数查询等。

3、注意: 使用的是数据库字段，不是 Java 属性。

4、条件参数说明

测试查询：

@Testpublic void testEntityWrapperSelect() {    //我们需要分页查询tbl_employee表中，年龄在18~50之间且性别为男且姓名为Tom的所有用户    List emps =employeeMapper.selectPage(new Page(1, 2),                new EntityWrapper()                .between("age", 18, 50)                .eq("gender", 1)                .eq("last_name", "Tom")            );    System.out.println(emps);        //我们需要分页查询tbl_employee表中，年龄在18~50之间且性别为男且姓名为Tom的所有用户    List emps3 = employeeMapper.selectPage(                    new Page(1,2),                        Condition.create()                        .between("age", 18, 50)                        .eq("gender", "1")                        .eq("last_name", "Tom")                        );    System.out.println(emps3);            // 查询tbl_employee表中， 性别为女并且名字中带有"老师" 或者  邮箱中带有"a"    List emps1 = employeeMapper.selectList(            new EntityWrapper()            .eq("gender", 0)            .like("last_name", "老师")            //.or()    // SQL: (gender = ? AND last_name LIKE ? OR email LIKE ?)            .orNew()   // SQL: (gender = ? AND last_name LIKE ?) OR (email LIKE ?)            .like("email", "a")            );    System.out.println(emps1);    //查询性别为女的, 根据age进行排序(asc/desc), 简单分页    List emps2  = employeeMapper.selectList(            new EntityWrapper()            .eq("gender", 0)            .orderBy("age") //默认是升序            //.orderDesc(Arrays.asList(new String [] {"age"}))            .last("desc limit 1,3") //在sql最后拼接            );    System.out.println(emps2);}

控制台输出：

selectPage方法：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE (age BETWEEN ? AND ? AND gender = ? AND last_name = ?)
Parameters: 18(Integer), 50(Integer), 1(Integer), Tom(String)
Total: 1
[Employee [id=1, lastName=Tom, email=tom@atguigu.com, gender=1, age=22]]
selectPage使用Condition：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE (age BETWEEN ? AND ? AND gender = ? AND last_name = ?)
Parameters: 18(Integer), 50(Integer), 1(String), Tom(String)
Total: 1
[Employee [id=1, lastName=Tom, email=tom@atguigu.com, gender=1, age=22]]
selectList使用or：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE (gender = ? AND last_name LIKE ? OR email LIKE ?)
Parameters: 0(Integer), %老师%(String), %a%(String)
Total: 3
[Employee [id=1, lastName=Tom, email=tom@atguigu.com, gender=1, age=22], Employee [id=2, lastName=Jerry, email=jerry@atguigu.com, gender=0, age=25], Employee [id=7, lastName=王五, email=xz@sina.com, gender=0, age=null]]
selectList使用orNew：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE (gender = ? AND last_name LIKE ?) OR (email LIKE ?)
Parameters: 0(Integer), %老师%(String), %a%(String)
Total: 3
[Employee [id=1, lastName=Tom, email=tom@atguigu.com, gender=1, age=22], Employee [id=2, lastName=Jerry, email=jerry@atguigu.com, gender=0, age=25], Employee [id=7, lastName=王五, email=xz@sina.com, gender=0, age=null]]
selectList使用orderBy：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE (gender = ?) ORDER BY age
Parameters: 0(Integer)
Total: 2
[Employee [id=7, lastName=王五, email=xz@sina.com, gender=0, age=null], Employee [id=2, lastName=Jerry, email=jerry@atguigu.com, gender=0, age=25]]
selectList使用orderDesc：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE (gender = ?) ORDER BY age DESC
Parameters: 0(Integer)
Total: 2
[Employee [id=2, lastName=Jerry, email=jerry@atguigu.com, gender=0, age=25], Employee [id=7, lastName=王五, email=xz@sina.com, gender=0, age=null]]
selectList使用last：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE (gender = ?) ORDER BY age desc limit 1,3
Parameters: 0(Integer)
Total: 1
[Employee [id=7, lastName=王五, email=xz@sina.com, gender=0, age=null]]

测试修改：

@Testpublic void testEntityWrapperUpdate() {    Employee employee = new Employee();    employee.setLastName("王五");    employee.setEmail("cls@sina.com");    employee.setGender(0);    employeeMapper.update(employee,                new EntityWrapper()                .eq("last_name", "Tom")                .eq("age", 44)                );}

控制台输出：

Preparing: UPDATE tbl_employee SET last_name=?, email=?, gender=? WHERE (last_name = ? AND age = ?)
Parameters: 王五(String), cls@sina.com(String), 0(Integer), Tom(String), 44(Integer)
Updates: 0

测试删除：

@Testpublic void testEntityWrapperDelete() {    employeeMapper.delete(                new EntityWrapper()                .eq("last_name", "Tom")                .eq("age", 22)            );}

控制台输出：

Preparing: DELETE FROM tbl_employee WHERE (last_name = ? AND age = ?)
Parameters: Tom(String), 22(Integer)
Updates: 1

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