MyBatis-Plus中使用EntityWrappe进行列表数据倒序设置方式
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]]
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
以上为个人经验，希望能给大家一个参考，也希望大家多多支持编程网。
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