java-jdbc

JDBC

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

String driverClassName = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&useSSL=false";
String user = "user01";
String password = "user01";
	
Class.forName(driverClassName).newInstance();
Connection con = DriverManager.getConnection(url, user, password);

// 插入 
String sql = "insert into user(name, password, age) values (?, ?, ?) ;";
PreparedStatement pst = con.prepareStatement(sql);
pst.setString(1, name);
pst.setString(2, password);
pst.setInt(3, age);
num = pst.executeUpdate();
pst.close();
con.close();			
			
// 查询
String sql = "select count(*) as count from table_user ;";
PreparedStatement pst = secondCon.prepareStatement(sql);
ResultSet rs = pst.executeQuery();
while (rs.next()) {
	// TODO
}			
rs.close();
pst.close();
con.close();

jdbc-pool

Tomcat 在 7.0 以前的版本都是使用 commons-dbcp 做为连接池的实现，但是 dbcp 饱受诟病，原因有：

dbcp 是单线程的，为了保证线程安全会锁整个连接池
dbcp 性能不佳
dbcp 太复杂，超过 60 个类
dbcp 使用静态接口，在 JDK 1.6 编译有问题
dbcp 发展滞后

因此很多人会选择一些第三方的连接池组件，例如 c3p0 , bonecp, druid (@wenshao ) 等。

为此，Tomcat 从 7.0 开始引入一个新的模块：Tomcat jdbc pool

tomcat jdbc pool 近乎兼容 dbcp ，性能更高
异步方式获取连接
tomcat jdbc pool 是 tomcat 的一个模块，基于 tomcat JULI，使用 Tomcat 的日志框架
使用 javax.sql.PooledConnection 接口获取连接
支持高并发应用环境
超简单，核心文件只有8个，比 c3p0 还
更好的空闲连接处理机制
支持 JMX
支持 XA Connection

tomcat jdbc pool 的优点远不止这些，详情请看 官网。

tomcat jdbc pool 可在 Tomcat 中直接使用，也可以在独立的应用中使用。

在独立的应用中使用

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

import org.apache.tomcat.jdbc.pool.DataSource;
import org.apache.tomcat.jdbc.pool.PoolProperties;

public class SimplePOJOExample {

  public static void main(String[] args) throws Exception {
	  PoolProperties p = new PoolProperties();
	  p.setUrl("jdbc:mysql://localhost:3306/mysql");
	  p.setDriverClassName("com.mysql.jdbc.Driver");
	  p.setUsername("root");
	  p.setPassword("password");
	  p.setJmxEnabled(true);
	  p.setTestWhileIdle(false);
	  p.setTestOnBorrow(true);
	  p.setValidationQuery("SELECT 1");
	  p.setTestOnReturn(false);
	  p.setValidationInterval(30000);
	  p.setTimeBetweenEvictionRunsMillis(30000);
	  p.setMaxActive(100);
	  p.setInitialSize(10);
	  p.setMaxWait(10000);
	  p.setRemoveAbandonedTimeout(60);
	  p.setMinEvictableIdleTimeMillis(30000);
	  p.setMinIdle(10);
	  p.setLogAbandoned(true);
	  p.setRemoveAbandoned(true);
	  p.setJdbcInterceptors(
		"org.apache.tomcat.jdbc.pool.interceptor.ConnectionState;"+
		"org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer");
	  DataSource datasource = new DataSource();
	  datasource.setPoolProperties(p);

	  Connection con = null;
	  try {
		con = datasource.getConnection();
		Statement st = con.createStatement();
		ResultSet rs = st.executeQuery("select * from user");
		int cnt = 1;
		while (rs.next()) {
			System.out.println((cnt++)+". Host:" +rs.getString("Host")+
			  " User:"+rs.getString("User")+" Password:"+rs.getString("Password"));
		}
		rs.close();
		st.close();
	  } finally {
		if (con!=null) try {con.close();}catch (Exception ignore) {}
	  }
  }

}

异步获取连接

Connection con = null;
try {
  Future<Connection> future = datasource.getConnectionAsync();
  while (!future.isDone()) {
      System.out.println("Connection is not yet available. Do some background work");
      try {
	  Thread.sleep(100); //simulate work
      }catch (InterruptedException x) {
	  Thread.currentThread().interrupted();
      }
  }
  con = future.get(); //should return instantly
  Statement st = con.createStatement();
  ResultSet rs = st.executeQuery("select * from user");

<dependency>  
	<groupId>org.apache.tomcat</groupId>  
	<artifactId>tomcat-jdbc</artifactId>  
	<version>7.0.29</version>  
</dependency>  
<dependency>  
	<groupId>org.apache.tomcat</groupId>  
	<artifactId>tomcat-juli</artifactId>  
	<version>7.0.29</version>  
</dependency>  
<!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-jdbc -->
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat-jdbc</artifactId>
    <version>8.5.15</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-juli -->
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat-juli</artifactId>
    <version>8.5.15</version>
</dependency>

References

JDBC
[1] http://www.yiibai.com/jdbc/jdbc_quick_guide.html
[2] http://www.cnblogs.com/DreamDrive/p/5757693.html
[3] http://blog.csdn.net/whucyl/article/details/20838079
[4] http://javastudyeye.iteye.com/blog/835448

jdbc-pool
[1] https://stackoverflow.com/questions/24559468/neo4j-jdbc-connection-pool
[2] http://tomcat.apache.org/tomcat-7.0-doc/jdbc-pool.html
[3] https://www.oschina.net/question/12_36910
[4] https://github.com/alibaba/druid