最全面的jdbcUtils，总有一种适合你

附加jar包,TxQueryRunner.java文件,dbconfig.properties配置文件(点击链接下载):

　　https://files.cnblogs.com/files/xiaoming0601/jdbcUtils%E7%9B%B8%E5%85%B3jar%E5%8C%85.zip

 

1.普通的连接数据库,读取dbconfig.properties配置文件

　　

package cn.itcast.jdbcUtils;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class JdbcUtils {
    private static final String dbconfig = "dbconfig.properties";
    private static Properties prop = new Properties();
    static {    
        try {
            InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream(dbconfig);
            prop.load(in);
            Class.forName(prop.getProperty("driverClassName"));
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    public static Connection getConnection(){
        try {
            return DriverManager.getConnection(prop.getProperty("url"),prop.getProperty("username"),prop.getProperty("password"));
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }        
    }
}

2.使用简单的连接池,给出c3p0-config.xml配置文件

　　1.c3p0-config.xml配置文件:

  <?xml version="1.0" encoding="UTF-8" ?> 
- <c3p0-config>
- <!--  这是默认配置信息 
  --> 
- <default-config>
- <!--  连接四大参数配置 
  --> 
  <property name="jdbcUrl">jdbc:mysql://localhost:3306/mydb1</property> 
  <property name="driverClass">com.mysql.jdbc.Driver</property> 
  <property name="user">root</property> 
  <property name="password">123</property> 
- <!--  池参数配置 
  --> 
  <property name="acquireIncrement">3</property> 
  <property name="initialPoolSize">10</property> 
  <property name="minPoolSize">2</property> 
  <property name="maxPoolSize">10</property> 
  </default-config>
- <!--  专门为oracle提供的配置信息 
  --> 
- <named-config name="oracle-config">
  <property name="jdbcUrl">jdbc:mysql://localhost:3306/mydb1</property> 
  <property name="driverClass">com.mysql.jdbc.Driver</property> 
  <property name="user">root</property> 
  <property name="password">123</property> 
  <property name="acquireIncrement">3</property> 
  <property name="initialPoolSize">10</property> 
  <property name="minPoolSize">2</property> 
  <property name="maxPoolSize">10</property> 
  </named-config>
  </c3p0-config>

　　2.代码

package cn.itcast.jdbcUtils;

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

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class JdbcUtils2 {
    // 配置文件的默认配置！要求你必须给出c3p0-config.xml！！！
    private static ComboPooledDataSource dataSource = new ComboPooledDataSource();
    public static Connection getConnection() throws SQLException {
        return dataSource.getConnection();
    }
    public static DataSource getDataSource() {
        return dataSource;
    }
}

3.使用连接池,最全面的获取dataSource,connection以及释放connection的方法,并提供开启,提交回滚事务的方法

　　

package cn.itcast.jdbcUtils;

import java.sql.Connection;
import java.sql.SQLException;
import javax.sql.DataSource;
import com.mchange.v2.c3p0.ComboPooledDataSource;

public class JdbcUtils3 {
    private static DataSource dataSource = new ComboPooledDataSource();
    private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
    //获取数据源
    public static DataSource getDataSource(){
        return dataSource;
    }
    //获取连接
    public static Connection getConnection() throws SQLException{
        Connection conn = tl.get();
        if(conn==null){
            return dataSource.getConnection();
        }
        return conn;
    }
    //开启事物
    public static void beginTransaction() throws SQLException{
        Connection conn = tl.get();
        if(conn!=null){
            throw new SQLException("您已经开启了事务，在没有结束当前事务时，不能再开启事务");
        }
        conn = dataSource.getConnection();
        conn.setAutoCommit(false);
        tl.set(conn);//把当前线程的连接保存起来！
    }
    //提交事务
    public static void commitTransaction() throws SQLException{
        Connection conn = tl.get();
        if(conn==null){
            throw new SQLException("当前没有事务，所以不能提交");
        }
        conn.commit();
        conn.close();
        tl.remove();
    }
    //回滚事务
    public static void rollbackTransaction() throws SQLException{
        Connection conn = tl.get();
        if(conn==null){
            throw new SQLException("当前没有事务，所以不能回滚");
        }
        conn.rollback();
        conn.close();
        tl.remove();
    }
    //释放连接
    public static void releaseConnection(Connection connection) throws SQLException {
        Connection con = tl.get();
        /*
         * 判断它是不是事务专用，如果是，就不关闭！
         * 如果不是事务专用，那么就要关闭！
         */
        // 如果con == null，说明现在没有事务，那么connection一定不是事务专用的！
        if(con == null) connection.close();
        // 如果con != null，说明有事务，那么需要判断参数连接是否与con相等，若不等，说明参数连接不是事务专用连接
        if(con != connection) connection.close();
    }
}

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