JDBC获取连接、关闭连接的简单工具类2

package com.adam.dev.utils;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

/**
* @author adam.胡升阳
*
*/
public class JdbcByPropertiesUtil {
private static String filePath = "jdbc.properties";
private static JdbcByPropertiesUtil instance = null;

public JdbcByPropertiesUtil() {
super();
}

/**
* 单例方式创建对象
* @return
*/
public static JdbcByPropertiesUtil getInstance() {
if (instance == null) {
synchronized (JdbcByPropertiesUtil.class) {
if (instance == null) {
instance = new JdbcByPropertiesUtil();
}
}
}
return instance;
}

/**
* 读取properties文件中 数据库连接信息
* @param filePath
* add 2012-4-17
*/
public static Properties readPropertiesFile(){
String realFilePath = Thread.currentThread().getContextClassLoader().getResource("").getPath()+filePath;
Properties pros = new Properties();
try {
InputStream is = new BufferedInputStream(new FileInputStream(realFilePath));
pros.load(is);
} catch (Exception e) {
e.printStackTrace();
}
return pros;
}

/**
* 注册驱动
* 静态代码块 用于启动web服务器时加载驱动
*/
static{
Properties pros = readPropertiesFile();
String className = (String) pros.get("className");
try {
Class.forName(className).newInstance();
} catch (Exception e) {
e.printStackTrace();
}
}

/**
* 获取数据库连接
* modify 2012-4-17
* @param con
* @return
*/
public Connection getConnection(){
Properties pros = readPropertiesFile();
String url = (String) pros.get("url");
String user = (String) pros.get("user");
String password = (String) pros.get("password");
Connection conn = null;
try {
conn = DriverManager.getConnection(url,user,password);
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}

/**
*  依次关闭ResultSet、Statement、Connection
*  若对象不存在则创建一个空对象
* @param rs
* @param st
* @param pst
* @param conn
*/
public void close(ResultSet rs,Statement st,Connection conn){
if(rs != null){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
} finally{
if(st != null){
try {
st.close();
} catch (SQLException e) {
e.printStackTrace();
} finally{
if(conn != null){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
}
}

/**
* 新增、修改、删除、查询记录(也可以改为有结果集ResultSet返回的查询方法)
* @param sql
* @throws
*/
public void execute(String sql){
JdbcByPropertiesUtil jbpu = getInstance();
Connection conn = null;
PreparedStatement pst = null;
try {
conn = jbpu.getConnection();
conn.setAutoCommit(false);
pst = conn.prepareStatement(sql);
pst.execute();
conn.commit();
} catch (Exception e) {
try {
conn.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
e.printStackTrace();
} finally{
//Statement st = null;
ResultSet rs = null;
jbpu.close(rs, pst, conn);
}
}

/**
* 新增、修改、删除记录
* @param sql
* @throws
*/
public void executeUpdate(String sql) {
JdbcByPropertiesUtil jbpu = getInstance();
Connection conn = null;
PreparedStatement pst = null;
try {
conn = jbpu.getConnection();
conn.setAutoCommit(false);
pst = conn.prepareStatement(sql);
pst.executeUpdate();
conn.commit();
} catch (Exception e) {
try {
conn.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
e.printStackTrace();
} finally{
//Statement st = null;
ResultSet rs = null;
jbpu.close(rs, pst, conn);
}
}

}