Java JDBC高级特性

Posted 2020-07-03 luoxn28

 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

 1 package server;
 2 
 3 import java.sql.Connection;
 4 import java.sql.DriverManager;
 5 import java.sql.ResultSet;
 6 import java.sql.Statement;
 7 
 8 import com.mysql.jdbc.PreparedStatement;
 9 
10 public class DemoJDBC {
11     public static void main(String[] args) throws Exception {
12         // 加载驱动类
13         Class.forName("com.mysql.jdbc.Driver");
14     
15         // 通过DriverManager获取数据库连接
16         String url = "jdbc:mysql://192.168.1.150/test";
17         String user = "teamtalk";
18         String password = "123456";
19         Connection connection = (Connection) DriverManager.getConnection(
20                 url, user, password);
21         
22         String sql1 = "DROP TABLE IF EXISTS people";
23         String sql2 = "CREATE TABLE people(id int, name varchar(20))";
24         String sql3 = "INSERT people VALUES(2, \'hdu\')";
25         String sql4 = "UPDATE people SET id = 1";
26         Statement statement = (Statement) connection.createStatement();
27         statement.addBatch(sql1);
28         statement.addBatch(sql2);
29         statement.addBatch(sql3);
30         statement.addBatch(sql4);
31         statement.executeBatch();
32         
33         ResultSet resultSet = statement.executeQuery("SELECT * from people");
34         while (resultSet.next()) {
35             System.out.println(resultSet.getString(1) + " " + resultSet.getString(2));
36         }
37     }
38 }

PreparedStatement批处理

 1 package server;
 2 
 3 import java.sql.Connection;
 4 import java.sql.DriverManager;
 5 import java.sql.ResultSet;
 6 import java.sql.Statement;
 7 
 8 import com.mysql.jdbc.PreparedStatement;
 9 
10 public class DemoJDBC {
11     public static void main(String[] args) throws Exception {
12         // 加载驱动类
13         Class.forName("com.mysql.jdbc.Driver");
14     
15         // 通过DriverManager获取数据库连接
16         String url = "jdbc:mysql://192.168.1.150/test";
17         String user = "teamtalk";
18         String password = "123456";
19         Connection connection = (Connection) DriverManager.getConnection(
20                 url, user, password);
21         
22         PreparedStatement statement =  (PreparedStatement) connection.prepareStatement("INSERT people VALUES(?,?)");
23         for (int i = 1; i < 4; i++) {
24             statement.setInt(1, i);
25             statement.setString(2, "hdu" + i);
26             statement.addBatch();
27         }
28         statement.executeBatch();
29         
30         ResultSet resultSet = statement.executeQuery("SELECT * from people");
31         while (resultSet.next()) {
32             System.out.println(resultSet.getString(1) + " " + resultSet.getString(2));
33         }
34     }
35 }

 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：

1 setAutoCommit(boolean autoCommit); // 设置是否自动提交事务
2 commit(); // 提交事务
3 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。

 1 package demo.jdbc;
 2 
 3 import java.sql.DriverManager;
 4 import java.sql.ResultSet;
 5 import java.sql.SQLException;
 6 
 7 import com.mysql.jdbc.Connection;
 8 import com.mysql.jdbc.PreparedStatement;
 9 import com.mysql.jdbc.Statement;
10 
11 public class FirstJDBC {
12     public static void main(String[] args) throws ClassNotFoundException, SQLException, InterruptedException {
13         Connection connection = null;
14         try {
15             // 加载驱动类
16             Class.forName("com.mysql.jdbc.Driver");
17         
18             // 通过DriverManager获取数据库连接
19             String url = "jdbc:mysql://192.168.1.150/test";
20             String user = "teamtalk";
21             String password = "123456";
22             connection = (Connection) DriverManager.getConnection(
23                     url, user, password);
24             // 关闭事务的自动提交
25             connection.setAutoCommit(false);
26             
27             Statement statement = (Statement) connection.createStatement();
28             PreparedStatement statement1 = (PreparedStatement) connection.prepareStatement("INSERT people VALUES(?, ?)");
29             PreparedStatement statement2 = (PreparedStatement) connection.prepareStatement("INSERT people VALUES(?, ?)");
30             
31             statement1.setInt(1, 1);
32             statement1.setString(2, "hdu1");
33             statement2.setInt(1, 2);
34             statement2.setString(2, "hdu2");
35             
36             statement1.executeUpdate();
37             statement2.executeUpdate();
38             
39             ResultSet resultSet = statement.executeQuery("SELECT * from people");
40             while (resultSet.next()) {
41                 System.out.println(resultSet.getString(1) + " " + resultSet.getString(2));
42             }
43         }
44         catch (Exception e) {
45             // 回滚事务
46             connection.rollback();
47             e.printStackTrace();
48         }
49     }
50 }

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。

 1 package server;
 2 
 3 import java.sql.Connection;
 4 import java.sql.ResultSet;
 5 import java.sql.SQLException;
 6 import java.sql.Statement;
 7 
 8 import javax.sql.DataSource;
 9 
10 import org.apache.commons.dbcp2.BasicDataSource;
11 
12 //import com.mysql.jdbc.Statement;
13 
14 public class DemoDBCP {
15     public static DataSource ds = null;
16     
17     static {
18         // 获取DBCP数据源实现类
19         BasicDataSource bds = new BasicDataSource();
20         // 设置连接池配置信息
21         bds.setDriverClassName("com.mysql.jdbc.Driver");
22         bds.setUrl("jdbc:mysql://192.168.1.150/test");
23         bds.setUsername("teamtalk");
24         bds.setPassword("123456");
25         // 设置连接池参数
26         bds.setInitialSize(5);
27         bds.setMaxTotal(5);
28         ds = bds;
29     }
30     
31     public static void main(String[] args) throws SQLException {
32         Connection connection = (Connection) ds.getConnection();
33         java.sql.DatabaseMetaData metaData = connection.getMetaData();
34         
35         System.out.println(metaData.getURL());
36         System.out.println(metaData.getUserName());
37         System.out.println(metaData.getDriverName());
38         
39         Statement statement = (Statement) connection.createStatement();
40         ResultSet resultSet = statement.executeQuery("SELECT * from people");
41         while (resultSet.next()) {
42             System.out.println(resultSet.getString(1) + " " + resultSet.getString(2));
43         }
44     }
45 }

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：

 1 <?xml version="1.0" encoding="UTF-8"?>  
 2 <c3p0-config>  
 3     <default-config>  
 4         <property name="jdbcUrl">jdbc:mysql://192.168.1.150/test</property>  
 5         <property name="driverClass">com.mysql.jdbc.Driver</property>  
 6         <property name="user">teamtalk</property>  
 7         <property name="password">123456</property>  
 8   
 9         <property name="checkoutTimeout">3000</property>  
10         <property name="idleConnectionTestPeriod">30</property>  
11         <property name="initialPoolSize">10</property>  
12         <property name="maxIdleTime">30</property>  
13         <property name="maxPoolSize">100</property>  
14         <property name="minPoolSize">10</property>  
15         <property name="maxStatements">200</property>  
16     </default-config>
17     
18     <named-config name="demo">  
19         <property name="jdbcUrl">jdbc:mysql://192.168.1.150/test</property>  
20         <property name="driverClass">com.mysql.jdbc.Driver</property>  
21         <property name="user">teamtalk</property>  
22         <property name="password">123456</property>  
23   
24         <property name="checkoutTimeout">3000</property>  
25         <property name="idleConnectionTestPeriod">30</property>  
26         <property name="initialPoolSize">10</property>  
27         <property name="maxIdleTime">30</property>  
28         <property name="maxPoolSize">100</property>  
29         <property name="minPoolSize">10</property>  
30         <property name="maxStatements">200</property>  
31     </named-config>
32     
33 </c3p0-config>  

 1 package server;
 2 
 3 import java.sql.Connection;
 4 import java.sql.SQLException;
 5 
 6 import javax.sql.DataSource;
 7 
 8 import com.mchange.v2.c3p0.ComboPooledDataSource;
 9 
10 public class DemoDBCP {
11     public static DataSource ds = null;
12     
13     static {
14         ComboPooledDataSource cpds = new ComboPooledDataSource();
15         ds = cpds;
16     }
17     
18     public static void main(String[] args) throws SQLException {
19         Connection connection = (Connection) ds.getConnection();
20         java.sql.DatabaseMetaData metaData = connection.getMetaData();
21         
22         System.out.println(metaData.getURL());
23         System.out.println(metaData.getUserName());
24         System.out.println(metaData.getDriverName());
25     }
26 }

 参考

Java JDBC基础学习小结