jdbc链接mysql的第二个例子。使用properties文件存放连接信息。使用jar文件一个

该例子将jdbc的链接信息封装到properties文件中。并将jdbc的基本使用框架提取到一个jdbcUtils类中。简化了jdbc操作数据库的操作。

JdbcUtil工具类：

package com.xiaohui.jdbc;

import java.io.IOException;
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 final class JdbcUtil {
private static String url;//数据库链接字符串
private static String user;//用户名
private static String pass;//密码
private static String driver;//数据库驱动
//加载类时，先将jdbc链接数据库信息获取并赋值
static {
Properties prop = new Properties();
InputStream in = JdbcUtil.class.getClassLoader().getResourceAsStream("com/xiaohui/jdbc/info.properties");
try {
prop.load(in);
} catch (IOException e) {
e.printStackTrace();
}
url = prop.getProperty("url");
user = prop.getProperty("user");
pass = prop.getProperty("pass");
driver = prop.getProperty("driver");
}
static{
try {
Class.forName(driver);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
//取得链接
public static Connection getMySqlConnection(){
Connection conn=null;
try {
conn = DriverManager.getConnection(url,user,pass);
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
//关闭结果集
public static  void close(ResultSet rs){
if(rs!=null){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
//关闭封装SQl命令的对象
public static  void close(Statement state){
if(state!=null){
try {
state.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
//关闭链接
public static  void close(Connection conn){
if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}

当很很多用户同时操作数据库时，获取到的都是一个conn链接对象。这样肯定不行。为了让每个线程都对应唯一的conn的链接对象可对上面的工具类做如下修改：

package com.xiaohui.jdbc.util;

import java.io.IOException;
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 final class JdbcUtil {
private static String url;
private static String user;
private static String pass;
private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
private static String driver;
static {
Properties prop = new Properties();
InputStream in = JdbcUtil.class.getClassLoader().getResourceAsStream(
"com/xiaohui/jdbc/config/info.properties");
try {
prop.load(in);
} catch (IOException e) {
e.printStackTrace();
}
url = prop.getProperty("url");
user = prop.getProperty("user");
pass = prop.getProperty("pass");
driver = prop.getProperty("driver");
}
static {
try {
Class.forName(driver);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}

// 让每个线程都对应唯一的一个Connection 对象
public static Connection getMySqlConnection() {
Connection conn = tl.get();
if(conn==null){
//第一次启动该线程没有绑定conn
try {
conn = DriverManager.getConnection(url, user, pass);
//将conn绑定到tl中。
tl.set(conn);
} catch (SQLException e) {
e.printStackTrace();
}
}
return conn;
}

public static void close(ResultSet rs) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}

public static void close(Statement state) {
if (state != null) {
try {
state.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}

public static void close(Connection conn) {
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}

public static void begin() {
Connection conn = getMySqlConnection();
try {
conn.setAutoCommit(false);
} catch (SQLException e) {
e.printStackTrace();
}
}

public static void commit() {
Connection conn = getMySqlConnection();
try {
conn.commit();
} catch (SQLException e) {
e.printStackTrace();
}
}

public static void rollback() {
Connection conn = getMySqlConnection();
try {
conn.rollback();
} catch (SQLException e) {
e.printStackTrace();
}
}

public static void closeConnection() {
Connection conn = getMySqlConnection();
JdbcUtil.close(conn);
//将该线程与所绑定的Connection对象分离
tl.remove();
}
}

简单的测试一：

package com.xiaohui.jdbc;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
public class JdbcDemo3 {
public static void main(String[] args) throws ClassNotFoundException {
Connection conn = null;
Statement state = null;
ResultSet rs = null;
String sqlstr = "select * from employee";
try {
conn = JdbcUtil.getMySqlConnection();
state = conn.createStatement();
rs = state.executeQuery(sqlstr);
while (rs.next()) {
int id = rs.getInt("id");
String name = rs.getString("name");
String sex = rs.getString("sex");
float salary = rs.getFloat("salary");
System.out.println(id + ":" + name + ":" + sex + ":" + salary);
}
} catch (Exception e) {
} finally {
JdbcUtil.close(rs);
JdbcUtil.close(state);
JdbcUtil.close(conn);
}
}
}

配置文件：info.properties

url = jdbc:mysql://127.0.0.1:3306/mysql3

user = root

pass = root

driver =com.mysql.jdbc.Driver

使用到的jar文件：mysql-connector-java-5.1.22-bin.jar