MyBatis：MyBatis-Plus条件构造器EntityWrapper

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:

查询测试

@Test
public void testEntityWrapperSelect() {


1.    //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);
    

2.    //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);
        


3.    // 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);



4.    //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);
}

日志输出：

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]]

修改测试

@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)
                );
}

日志输出：

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

删除测试

@Test
public void testEntityWrapperDelete() {
    employeeMapper.delete(
                new EntityWrapper<Employee>()
                .eq("last_name", "Tom")
                .eq("age", 22)
            );
}

日志输出：

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

文章转载至：https://blog.csdn.net/lizhiqiang1217/article/details/89738906