JDBC模拟连接池、C3P0获取链接和最终的JdbcUtils工具类的版本

一丶模拟连接池获取连接：

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package jdbc_util; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.List; import java.util.Properties; //模式连接池的操作 public class JdbcUtil02 { private static String driver = null; private static String url = null; private static String username = null; private static String password = null; private static int Normal = 10; //初始化连接数 private static int MAX = 20; //最大的连接数 private static int MIN = 5; //最小的连接数 @SuppressWarnings("unused") private static int NUM = 0; //当前连接数 //使用集合 模式连接池 private static List<Connection> pool = new ArrayList<Connection>(); //初始化连接池 static{ //读取参数 Properties p = new Properties(); try { FileInputStream fis = new FileInputStream(new File("src//jdbc.properties")); p.load(fis); driver = p.getProperty("driver"); url = p.getProperty("url"); username = p.getProperty("username"); password = p.getProperty("password"); //加载驱动 Class.forName(driver); //初始化连接池 for(int i = 0; i < Normal; i++){ pool.add(createConnection()); NUM++; } } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } //从数据库中获取物理链接 private static Connection createConnection(){ Connection conn = null; try { conn = DriverManager.getConnection(url, username, password); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return conn; } //获取链接的方法 public static Connection getConnection(){ if(pool.size() > MIN){ return pool.remove(0); }else{ if(pool.size() <= MAX){ Connection conn = createConnection(); NUM++; return conn; }else{ throw new RuntimeException("链接已经用完，请等待..."); } } } public static void close(Connection conn,Statement stat, ResultSet rs){ if(conn != null){ //关闭 实际上是将连接 放回到连接池中 pool.add(conn); } try { if(stat != null){ stat.close(); } if(rs != null){ rs.close(); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }

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properties文件的情况：

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二丶使用C3P0获取连接

1.首先加载C3P0的驱动包，

2.再将C3P0的配置文件放在src的目录下，

3.改配置文件里面的密码，和需要访问数据库的名字

代码如下：

package jdbc_util; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import javax.sql.DataSource; import com.mchange.v2.c3p0.ComboPooledDataSource; public class JdbcUtil03 { private static DataSource ds ; //数据源 //加载驱动 static{ //读配置文件 ds = new ComboPooledDataSource(); } public static Connection getConnection(){ Connection conn = null; try { conn = ds.getConnection(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return conn; } public static void close(Connection conn,Statement stat,ResultSet rs){ if(conn != null){ try { conn.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } if(stat != null){ try { stat.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } if(rs != null){ try { rs.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }

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三丶最终的JDBCUtil工具类

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需要加载的jar的包有一下：