MyBatis-Plus中使用EntityWrappe进行列表数据倒序设置方式代码示例

本篇文章小编给大家分享一下MyBatis-Plus中使用EntityWrappe进行列表数据倒序设置方式代码示例，文章代码介绍的很详细，小编觉得挺不错的，现在分享给大家供大家参考，有需要的小伙伴们可以来看看。

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：

@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 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：

@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()
                .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()
                .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