Mybatis的接口函数能不能进行重载？
- mybatis版本：3.4x
- java版本：java 8
语法层面
1、接口的方法可以进行重载，因为 java 语法可以让接口函数进行重载。
Mybatis框架方面
1、结论：可以有条件的进行重载。
2、为什么会有这个问题？：mybatis里面将接口里面的方法名称和配置文件里面的id属性进行唯一配对，在同一个命名空间下只能有一个id，那么所有函数名称相同的重载函数都会被绑定到一个id上，所以，如果要实现函数的重载，必须让一个SQL语句去适应多个函数的参数，如果是单纯的重载是肯定不行的（重载函数的定义就是参数相关），但是得益于mybatis的多种传参方式和隐性的分页功能，可以在接口里面进行函数重载，但是还是需要将所有的重载函数适配到同一个id的SQL上面去，仍然有很大的局限性，并不是可以随意的进行重载。
测试
1、数据库环境
DROP TABLE IF EXISTS sys_user;
CREATE TABLE sys_user(
id BIGINT NOT NULL AUTO_INCREMENT COMMENT '用户的ID',
user_name VARCHAR(50) COMMENT '用户名称',
user_password VARCHAR(50) COMMENT '密码',
user_email VARCHAR(50) COMMENT '邮箱',
user_info TEXT COMMENT '简介',
head_img BLOB COMMENT '头像',
create_time DATETIME COMMENT '创建时间',
PRIMARY KEY (id)
)DEFAULT CHARSET utf8;
ALTER TABLE sys_user COMMENT '用户表';
INSERT INTO sys_user VALUES ('1','admin','123456','[email protected]','管理员',null,'2016-04-01 17:00:58');
INSERT INTO sys_user VALUES ('1001','test','123456','[email protected]','测试用户',null,'2016-04-01 17:01:52');
2、实体类
public class SysUser {
private Long id;
private String userName;
private String userPassword;
private String userEmail;
private String userInfo;
private byte[] headImg;
private Date createTime;
public SysUser(){
}
/**setter and getter*/
}
3、测试
3.1、测试模板代码
public class SysUserDaoTest {
private static SqlSessionFactory sqlSessionFactory;
private SqlSession sqlSession;
@BeforeClass
public static void beforeClass(){
String resource = "plus/mybatis-config.xml";
try{
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
}catch(IOException e){
e.printStackTrace();
}
}
@Before
public void before(){
//事物手动提交
sqlSession = sqlSessionFactory.openSession(false);
}
@After
public void after(){
//回滚事物
sqlSession.rollback(true);
//关闭会话
sqlSession.close();
}
}
3.2、测试场景一
重载实现分页、参数类型转换实现重载。
3.2.1、接口
public interface SysUserDao {
SysUser selectById(Long id);
List selectById(Long id,RowBounds rowBound);
}
3.2.2、mapper配置文件
3.3、测试场景二
参数传递方式实现重载，map参数传递和固定参数名的参数传递方式
3.3.1、接口
public interface SysUserDao {
SysUser selectByCondition(@Param("id")Long id,@Param("userName")String userName,@Param("userPassword")String userPassword);
SysUser selectByCondition(Map params);
}
3.3.2、mapper配置文件
3.4、完整的测试代码
package plus.dao;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.*;
import org.junit.*;
import plus.pojo.SysUser;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class SysUserDaoTest {
private static SqlSessionFactory sqlSessionFactory;
private SqlSession sqlSession;
@BeforeClass
public static void beforeClass(){
String resource = "plus/mybatis-config.xml";
try{
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
}catch(IOException e){
e.printStackTrace();
}
}
@Before
public void before(){
//事物手动提交
sqlSession = sqlSessionFactory.openSession(false);
}
@After
public void after(){
//回滚事物
sqlSession.rollback(true);
//关闭会话
sqlSession.close();
}
@Test
public void selectById(){
SysUserDao sysUserDao = sqlSession.getMapper(SysUserDao.class);
SysUser sysUser = sysUserDao.selectById(1L);
Assert.assertEquals("admin",sysUser.getUserName());
SysUser sysUser1 = sysUserDao.selectById("1");
Assert.assertEquals("admin",sysUser1.getUserName());
/*
plus.dao.SysUserDao.selectById - ==> Preparing: SELECT * FROM sys_user WHERE id = ?;
plus.dao.SysUserDao.selectById - ==> Parameters: 1(Long)
plus.dao.SysUserDao.selectById - <== Total: 1
plus.dao.SysUserDao.selectById - ==> Preparing: SELECT * FROM sys_user WHERE id = ?;
plus.dao.SysUserDao.selectById - ==> Parameters: 1(String)
plus.dao.SysUserDao.selectById - <== Total: 1
*/
RowBounds rowBound = new RowBounds(0,2);
List sysUsers = sysUserDao.selectById(1L,rowBound);
Assert.assertEquals(1,sysUsers.size());
/*
plus.dao.SysUserDao.selectById - ==> Preparing: SELECT * FROM sys_user WHERE id = ?;
plus.dao.SysUserDao.selectById - ==> Parameters: 1(Long)
plus.dao.SysUserDao.selectById - <== Total: 1
*/
}
@Test
public void selectByCondition(){
SysUserDao sysUserDao = sqlSession.getMapper(SysUserDao.class);
SysUser sysUser = sysUserDao.selectByCondition(1L,"admin","123456");
Assert.assertEquals("[email protected]",sysUser.getUserEmail());
/*
plus.dao.SysUserDao.selectByCondition - ==> Preparing: SELECT * FROM sys_user WHERE id = ? AND user_name = ? AND user_password = ?;
plus.dao.SysUserDao.selectByCondition - ==> Parameters: 1(Long), admin(String), 123456(String)
plus.dao.SysUserDao.selectByCondition - <== Total: 1
*/
Map params = new HashMap(3);
params.put("id",1L);
params.put("userName","admin");
params.put("userPassword","123456");
SysUser sysUser1 = sysUserDao.selectByCondition(params);
/*
plus.dao.SysUserDao.selectById - ==> Preparing: SELECT * FROM sys_user WHERE id = ?;
plus.dao.SysUserDao.selectById - ==> Parameters: 1(Long)
plus.dao.SysUserDao.selectById - <== Total: 1
*/
Assert.assertEquals("[email protected]",sysUser1.getUserEmail());
}
}
3.5、完整的mapper文件
3.6、完整的接口
public interface SysUserDao {
SysUser selectById(Long id);
List selectById(Long id,RowBounds rowBound);
SysUser selectById(String name);
SysUser selectByCondition(@Param("id")Long id,@Param("userName")String userName,@Param("userPassword")String userPassword);
SysUser selectByCondition(Map params);
}
MyBatis实现方法重载的小技巧
QuestionMapper.java
利用接口默认方法 default 实现
QuestionMapper.xml
利用动态sql对 userId 字段进行判断
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脚本之家。