接口中定义的方法在抽象类中实现(一)

今天在做一个dao工厂时遇到一个问题，就是对于数据库的连接到底在哪里关闭，在创建连接时是在dao父类中创建的，而关闭则不能在一个dao的方法中去完成，那样在使用这个dao实例的方法会报异常，看来还得为每个dao定义一个关闭连接的方法，而这个方法还得在接口中声明，，那样就得在每个实现中去实现一遍重复的代码了，试着把这个实现的代码提到一个抽象类中，在实现接口的子类中没有去覆写，也没有报错，嘿嘿，目的达到了，，原来实现一个接口又实现一个父类，接口中方法原来可以在继承的父类中实现。好吧贴一下代码。

[java]
dao接口：
package com.justsy.mdm.dao;

import java.sql.SQLException;

import com.justsy.mdm.permission.User;

public interface IUserDAO {

public User login(String name, String password) throws SQLException;


public void closeConnQuiet() ;
}

[java]
抽象父类：


package com.justsy.mdm.dao;

import java.sql.Connection;
import java.sql.SQLException;

import org.apache.log4j.Logger;

import com.justsy.mdm.util.DBManager;

public abstract class AbstractBaseDAO {

protected final Logger logger = Logger.getLogger(getClass());

protected final DBManager db = DBManager.getDbManager();

protected Connection conn;

public AbstractBaseDAO() throws SQLException, ClassNotFoundException {
conn = db.createConn();
}

/**
* 关闭连接，不捕获异常
*/
public void closeConnQuiet() {
if (conn != null) {
try {
conn.close() ;
logger.debug("close connection success!!") ;
} catch (SQLException e) {
logger.warn("close connection fail"+e) ;
//e.printStackTrace();
}
}
}
}

[java]
userDao实现类，这个类中就没有覆写closeConnQuiet方法

package com.justsy.mdm.dao.impl;

import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.justsy.mdm.dao.AbstractBaseDAO;
import com.justsy.mdm.dao.IUserDAO;
import com.justsy.mdm.permission.Resource;
import com.justsy.mdm.permission.Role;
import com.justsy.mdm.permission.User;
import com.justsy.mdm.permission.comparator.Function;
import com.justsy.mdm.permission.comparator.FunctionFactory;

public class UserDAO extends AbstractBaseDAO implements IUserDAO {

public UserDAO() throws SQLException, ClassNotFoundException {
super();
}

@Override
public User login(String name, String password) throws SQLException {
logger.debug("user login username:" + name + ",password:" + password);

String sql = "select * from user where name= and password= ";

PreparedStatement pstmt = db.prepare(conn, sql);
ResultSet rs = db.getResult(pstmt, new Object[] { name, password });
User user = null;
while (rs.next()) {
user = new User();
int userId = rs.getInt(1);
String userName = rs.getString("name");

user.setId(userId);
user.setName(userName);

sql = "select * from role where id in (select roleid from user_role where userid= )";

PreparedStatement rolePstmt = db.prepare(conn, sql);
ResultSet roleRs = db.getResult(rolePstmt, new Object[] { userId });
Role role = null;
while (roleRs.next()) {
role = new Role();
long roleId = roleRs.getLong("id");
String roleName = roleRs.getString("name");
role.setId(roleId);
role.setName(roleName);
// user中添加角色
user.getRol