Dao模式:
1. 新建一个dao的接口， 里面声明数据库访问规则.
2. 新建一个dao的实现类，具体实现早前定义的规则.
3. 直接使用实现.
代码如下:
UserDao:
package com.test.dao;
/**
* 定义操作数据库的方法
* <p>Title: UserDao</p>
* <p>Description: </p>
* <p>Company: www.itcast.cn</p>
* @version 1.0
*/
public interface UserDao {
//查询
void findAll();
}
UserDaoImpl:
package com.test.dao.impl;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import com.test.dao.UserDao;
import com.test.util.JDBCUtil;
public class UserDaoImpl implements UserDao {
/**
* 查询
* <p>Title: findAll</p>
* <p>Description: </p>
* @see com.test.dao.UserDao#findAll()
*/
Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
@Override
public void findAll() {
try {
connection = JDBCUtil.getConn();
statement = connection.createStatement();
String sql ="select * from user";
resultSet = statement.executeQuery(sql);
while(resultSet.next()){
String username = resultSet.getString("username");
String password = resultSet.getString("password");
System.out.println("username="+username+",password="+password);
}
} catch (Exception e) {
// TODO: handle exception
}finally{
JDBCUtil.close(connection, resultSet, statement);
}
}
}
JunitTest:
package com.test.example;
import org.junit.Test;
import com.test.dao.UserDao;
import com.test.dao.impl.UserDaoImpl;
public class JunitTest {
//查询
@Test
public void testFindAll(){
UserDao dao = new UserDaoImpl();
dao.findAll();
}
}
JDBCUtil:
package com.test.util;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class JDBCUtil {
static String driverClass = null;
static String url = null;
static String name = null;
static String password = null;
//读取jdbc.properties
static{
try {
//1.创建一个属性配置对象
Properties properties = new Properties();
//1.对应文件位于工程根目录
//InputStream is = new FileInputStream("jdbc.properties");
//2.使用类加载器,读取drc下的资源文件 对应文件位于src目录底下 建议使用
InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
//2.导入输入流,抓取异常
properties.load(is);
//3.读取属性
driverClass = properties.getProperty("driverClass");
url = properties.getProperty("url");
name = properties.getProperty("name");
password = properties.getProperty("password");
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
/**
* 注册驱动 建立参数
* <p>Title: close</p>
* <p>Description: </p>
* @param connection
* @param resultSet
* @param statement
*/
public static Connection getConn(){
Connection connection = null;
//2. 建立连接 参数一： 协议 + 访问的数据库 ， 参数二： 用户名 ， 参数三： 密码。
try {
//Class.forName(driverClass);可写可不写
//Class.forName(driverClass);
connection = DriverManager.getConnection(url, name, password);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return connection;
}
/**
* 释放资源
* <p>Title: close</p>
* <p>Description: </p>
* @param connection
* @param resultSet
* @param statement
*/
public static void close(Connection connection,ResultSet resultSet,Statement statement){
closeRS(resultSet);
closeSt(statement);
closeConn(connection);
}
public static void close(Connection connection,Statement statement){
closeSt(statement);
closeConn(connection);
}
private static void closeRS(ResultSet resultSet){
try {
if(resultSet !=null){
resultSet.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
resultSet = null;
}
}
private static void closeSt(Statement statement){
try {
if(statement !=null){
statement.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
statement = null;
}
}
private static void closeConn(Connection connection){
try {
if(connection !=null){
connection.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
connection = null;
}
}
}
jdbc.properties:
driverClass=com.mysql.jdbc.Driver
url = jdbc:mysql://localhost/jdbc
name = root
password = root数据库:
运行结果:
