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

博主:xiaoweixiaowei 2023-01-18 条评论

本篇内容主要讲解“MyBatis-Plus中怎么使用EntityWrappe进行列表数据倒序设置”,感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷,实用性强。下面就让小编来带大家学习“MyBatis-Plus中怎么使用EntityWrappe进行列表数据倒序设置”吧!

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<CompanyInfoEntity>() wrapper= new EntityWrapper<CompanyInfoEntity>();
 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<String, Object> params) {
        //EntityWrapper 可以封装bean参数
        String name=(String)params.get("name");
        Page<CompanyInfoEntity> page = this.selectPage(
                new Query<CompanyInfoEntity>(params).getPage(),
                new EntityWrapper<CompanyInfoEntity>()
                        .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:

@Test
public 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<Employee> emps =employeeMapper.selectPage(new Page<Employee>(1, 2),
                new EntityWrapper<Employee>()
                .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<Employee > emps3 = employeeMapper.selectPage(
                    new Page<Employee>(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<Employee> emps1 = employeeMapper.selectList(
            new EntityWrapper<Employee>()
            .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<Employee> emps2  = employeeMapper.selectList(
            new EntityWrapper<Employee>()
            .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]]

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

测试修改:

@Test
public void testEntityWrapperUpdate() {
    Employee employee = new Employee();
    employee.setLastName("王五");
    employee.setEmail("cls@sina.com");
    employee.setGender(0);
    employeeMapper.update(employee,
                new EntityWrapper<Employee>()
                .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:

@Test
public void testEntityWrapperDelete() {
    employeeMapper.delete(
                new EntityWrapper<Employee>()
                .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

到此,相信大家对“MyBatis-Plus中怎么使用EntityWrappe进行列表数据倒序设置”有了更深的了解,不妨来实际操作一番吧!这里是云网站,更多相关内容可以进入相关频道进行查询,关注我们,继续学习!

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发布于:2023-01-18,除非注明,否则均为 主机评测原创文章,转载请注明出处。