Java JDBC高级特性

1、JDBC批处理

实际开发中需要向数据库发送多条SQL语句，这时，如果逐条执行SQL语句，效率会很低，因此可以使用JDBC提供的批处理机制。Statement和PreparedStatemen都实现了批处理。测试表结构如下：

Statement批处理程序示例

 package server;

 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.ResultSet;
 import java.sql.Statement;

 import com.mysql.jdbc.PreparedStatement;

 public class DemoJDBC {
     public static void main(String[] args) throws Exception {
         // 加载驱动类
         Class.forName("com.mysql.jdbc.Driver");

         // 通过DriverManager获取数据库连接
         String url = "jdbc:mysql://192.168.1.150/test";
         String user = "teamtalk";
         String password = "123456";
         Connection connection = (Connection) DriverManager.getConnection(
                 url, user, password);

         String sql1 = "DROP TABLE IF EXISTS people";
         String sql2 = "CREATE TABLE people(id int, name varchar(20))";
         String sql3 = "INSERT people VALUES(2, 'hdu')";
         String sql4 = "UPDATE people SET id = 1";
         Statement statement = (Statement) connection.createStatement();
         statement.addBatch(sql1);
         statement.addBatch(sql2);
         statement.addBatch(sql3);
         statement.addBatch(sql4);
         statement.executeBatch();

         ResultSet resultSet = statement.executeQuery("SELECT * from people");
         while (resultSet.next()) {
             System.out.println(resultSet.getString(1) + " " + resultSet.getString(2));
         }
     }
 }

PreparedStatement批处理

 package server;

 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.ResultSet;
 import java.sql.Statement;

 import com.mysql.jdbc.PreparedStatement;

 public class DemoJDBC {
     public static void main(String[] args) throws Exception {
         // 加载驱动类
         Class.forName("com.mysql.jdbc.Driver");

         // 通过DriverManager获取数据库连接
         String url = "jdbc:mysql://192.168.1.150/test";
         String user = "teamtalk";
         String password = "123456";
         Connection connection = (Connection) DriverManager.getConnection(
                 url, user, password);

         PreparedStatement statement =  (PreparedStatement) connection.prepareStatement("INSERT people VALUES(?,?)");
         for (int i = 1; i < 4; i++) {
             statement.setInt(1, i);
             statement.setString(2, "hdu" + i);
             statement.addBatch();
         }
         statement.executeBatch();

         ResultSet resultSet = statement.executeQuery("SELECT * from people");
         while (resultSet.next()) {
             System.out.println(resultSet.getString(1) + " " + resultSet.getString(2));
         }
     }
 }

2、JDBC处理事务

针对JDBC处理事务的操作，在Connection接口中，提供了3个相关的方法，具体如下：

 setAutoCommit(boolean autoCommit); // 设置是否自动提交事务
 commit(); // 提交事务
 rollback(); // 撤销事务

将setAutoCommit()方法参数设置为false后，事务必须使用conn.commit()方法提交，而事务回滚不一定显式执行conn.rollback()。如果程序最后没有执行conn.commit()，事务也会回滚，一般是直接抛出异常，终止程序的正常执行。因此，通常情况下，会conn.rollback()语句放在catch语句块执行。

将setAutoCommit()方法参数设置为false后，如果没有提交事务，也就是没有调用conn.commit()方法，则数据库中的内容不会更新，修改的只是内存缓冲区中的数据。

 package demo.jdbc;

 import java.sql.DriverManager;
 import java.sql.ResultSet;
 import java.sql.SQLException;

 import com.mysql.jdbc.Connection;
 import com.mysql.jdbc.PreparedStatement;
 import com.mysql.jdbc.Statement;

 public class FirstJDBC {
     public static void main(String[] args) throws ClassNotFoundException, SQLException, InterruptedException {
         Connection connection = null;
         try {
             // 加载驱动类
             Class.forName("com.mysql.jdbc.Driver");

             // 通过DriverManager获取数据库连接
             String url = "jdbc:mysql://192.168.1.150/test";
             String user = "teamtalk";
             String password = "123456";
             connection = (Connection) DriverManager.getConnection(
                     url, user, password);
             // 关闭事务的自动提交
             connection.setAutoCommit(false);

             Statement statement = (Statement) connection.createStatement();
             PreparedStatement statement1 = (PreparedStatement) connection.prepareStatement("INSERT people VALUES(?, ?)");
             PreparedStatement statement2 = (PreparedStatement) connection.prepareStatement("INSERT people VALUES(?, ?)");

             statement1.setInt(1, 1);
             statement1.setString(2, "hdu1");
             statement2.setInt(1, 2);
             statement2.setString(2, "hdu2");

             statement1.executeUpdate();
             statement2.executeUpdate();

             ResultSet resultSet = statement.executeQuery("SELECT * from people");
             while (resultSet.next()) {
                 System.out.println(resultSet.getString(1) + " " + resultSet.getString(2));
             }
         }
         catch (Exception e) {
             // 回滚事务
             connection.rollback();
             e.printStackTrace();
         }
     }
 }

3、JDBC连接池

DBCP数据源

使用DBCP数据源需要使用3个jar包，分别是commons-dbcp.jar包(https://commons.apache.org/proper/commons-dbcp/download_dbcp.cgi)、commons-pool.jar(http://commons.apache.org/proper/commons-pool/download_pool.cgi)包和commons-logging.jar(http://commons.apache.org/proper/commons-logging/download_logging.cgi)包。以下程序示例是通过BasicDataSource类直接创建数据源对象。

 package server;

 import java.sql.Connection;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;

 import javax.sql.DataSource;

 import org.apache.commons.dbcp2.BasicDataSource;

 //import com.mysql.jdbc.Statement;

 public class DemoDBCP {
     public static DataSource ds = null;

     static {
         // 获取DBCP数据源实现类
         BasicDataSource bds = new BasicDataSource();
         // 设置连接池配置信息
         bds.setDriverClassName("com.mysql.jdbc.Driver");
         bds.setUrl("jdbc:mysql://192.168.1.150/test");
         bds.setUsername("teamtalk");
         bds.setPassword("123456");
         // 设置连接池参数
         bds.setInitialSize(5);
         bds.setMaxTotal(5);
         ds = bds;
     }

     public static void main(String[] args) throws SQLException {
         Connection connection = (Connection) ds.getConnection();
         java.sql.DatabaseMetaData metaData = connection.getMetaData();

         System.out.println(metaData.getURL());
         System.out.println(metaData.getUserName());
         System.out.println(metaData.getDriverName());

         Statement statement = (Statement) connection.createStatement();
         ResultSet resultSet = statement.executeQuery("SELECT * from people");
         while (resultSet.next()) {
             System.out.println(resultSet.getString(1) + " " + resultSet.getString(2));
         }
     }
 }

c3p0数据库连接池

c3p0是目前最流行的开源数据库连接池之一，它实现了DataSource数据源接口，支持JDBC2和JDB3的标准规范，易于扩展并且性能优越，著名的开源框架Hibernate和Spring使用功能的都是该数据源。c3p0连接数据库示例（通过配置文件方式），注意：配置文件名称必须是c3p0-config.xml，该文件必须放在工程bin目录下。下载地址：https://sourceforge.net/projects/c3p0/?source=typ_redirect

配置文件c3p0-config.xml为：

 <?xml version="1.0" encoding="UTF-8"?>
 <c3p0-config>
     <default-config>
         <property name="jdbcUrl">jdbc:mysql://192.168.1.150/test</property>
         <property name="driverClass">com.mysql.jdbc.Driver</property>
         <property name="user">teamtalk</property>
         <property name="password">123456</property>  

         <property name="checkoutTimeout">3000</property>
         <property name="idleConnectionTestPeriod">30</property>
         <property name="initialPoolSize">10</property>
         <property name="maxIdleTime">30</property>
         <property name="maxPoolSize">100</property>
         <property name="minPoolSize">10</property>
         <property name="maxStatements">200</property>
     </default-config>

     <named-config name="demo">
         <property name="jdbcUrl">jdbc:mysql://192.168.1.150/test</property>
         <property name="driverClass">com.mysql.jdbc.Driver</property>
         <property name="user">teamtalk</property>
         <property name="password">123456</property>  

         <property name="checkoutTimeout">3000</property>
         <property name="idleConnectionTestPeriod">30</property>
         <property name="initialPoolSize">10</property>
         <property name="maxIdleTime">30</property>
         <property name="maxPoolSize">100</property>
         <property name="minPoolSize">10</property>
         <property name="maxStatements">200</property>
     </named-config>

 </c3p0-config>  

 package server;

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

 import javax.sql.DataSource;

 import com.mchange.v2.c3p0.ComboPooledDataSource;

 public class DemoDBCP {
     public static DataSource ds = null;

     static {
         ComboPooledDataSource cpds = new ComboPooledDataSource();
         ds = cpds;
     }

     public static void main(String[] args) throws SQLException {
         Connection connection = (Connection) ds.getConnection();
         java.sql.DatabaseMetaData metaData = connection.getMetaData();

         System.out.println(metaData.getURL());
         System.out.println(metaData.getUserName());
         System.out.println(metaData.getDriverName());
     }
 }

参考

Java JDBC基础学习小结