20160409 javaweb 数据库连接池
1.自己编写数据库连接池：
package com.dzq.pool; import java.io.PrintWriter; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.SQLFeatureNotSupportedException; import java.util.LinkedList; import java.util.List; import java.util.logging.Logger; import javax.sql.DataSource; public class MyPool implements DataSource { private static List<Connection> pool=new LinkedList<Connection>(); static{ try{ Class.forName("com.mysql.jdbc.Driver"); for(int i=0;i<5;i++){ Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/database01?Unicode=true&characterEncoding=utf-8","root",""); pool.add(conn); } }catch(Exception e){ e.printStackTrace(); throw new RuntimeException(e); } } @Override public Connection getConnection() throws SQLException { if(pool.size()==0){ for(int i=0;i<3;i++){ Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/database01?Unicode=true&characterEncoding=utf-8","root",""); pool.add(conn); } } final Connection conn=pool.remove(0); //利用动态代理改造close方法 Connection proxy= (Connection) Proxy.newProxyInstance(conn.getClass().getClassLoader(), new Class[]{Connection.class}, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { if("close".equals(method.getName())){ //对于想改造的close方法，我们自己写 retConn(conn); return null; }else{ //对于不想改造的方法，用被代理者身上相同的方法 return method.invoke(conn, args); } } }); System.out.println("获取了一个连接，池里还剩"+pool.size()+"个连接"); return proxy; } private void retConn(Connection conn){ try { if(conn!=null&&conn.isClosed()){ pool.add(conn); System.out.println("还回了一个连接池里还剩"+pool.size()+"个连接"); } } catch (SQLException e) { e.printStackTrace(); } } @Override public Connection getConnection(String arg0, String arg1) throws SQLException { return null; } @Override public PrintWriter getLogWriter() throws SQLException { // TODO Auto-generated method stub return null; } @Override public int getLoginTimeout() throws SQLException { // TODO Auto-generated method stub return 0; } @Override public Logger getParentLogger() throws SQLFeatureNotSupportedException { // TODO Auto-generated method stub return null; } @Override public void setLogWriter(PrintWriter arg0) throws SQLException { // TODO Auto-generated method stub } @Override public void setLoginTimeout(int arg0) throws SQLException { // TODO Auto-generated method stub } @Override public boolean isWrapperFor(Class<?> iface) throws SQLException { // TODO Auto-generated method stub return false; } @Override public <T> T unwrap(Class<T> iface) throws SQLException { // TODO Auto-generated method stub return null; } }
2.开源数据源：
1.DBCP：
方式1：
BasicDataSource source = new BasicDataSource();
source.setDriverClassName("com.mysql.jdbc.Driver");
source.setUrl("jdbc:mysql:///day11");
source.setUsername("root");
source.setPassword("root");
方式2：
Properties prop = new Properties();
prop.load(new FileReader("dbcp.properties"));
BasicDataSourceFactory factory = new BasicDataSourceFactory();
DataSource source = factory.createDataSource(prop);
配置文件中：
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql:///day11
username=root
password=root
#<!-- 初始化连接 -->
initialSize=10
#最大连接数量
maxActive=50
#<!-- 最大空闲连接 -->
maxIdle=20
#<!-- 最小空闲连接 -->
minIdle=5
#<!-- 超时等待时间以毫秒为单位 6000毫秒/1000等于60秒 -->
maxWait=60000
代码如下：
package com.dzq.jdbc; import java.io.FileReader; import java.io.IOException; import java.io.InputStream; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.Properties; import javax.sql.DataSource; import org.apache.commons.dbcp.BasicDataSource; import org.apache.commons.dbcp.BasicDataSourceFactory; public class DBCPDemo { public static void main(String[] args) { Connection conn=null; PreparedStatement ps=null; ResultSet rs=null; try { Properties prop=new Properties(); prop.load(new FileReader("dbcp.properties")); /*BasicDataSource source=new BasicDataSource(); source.setDriverClassName("com.mysql.jdbc.Driver"); source.setUrl("jdbc:mysql://localhost:3306/database01?Unicode=true&characterEncoding=utf-8"); source.setUsername("root"); source.setPassword("");*/ BasicDataSourceFactory factory =new BasicDataSourceFactory(); DataSource source=factory.createDataSource(prop); conn=source.getConnection(); String sql="select * from account"; ps=conn.prepareStatement(sql); rs=ps.executeQuery(); while (rs.next()) { String name=rs.getString("name"); System.out.println(name); } } catch (Exception e) { e.printStackTrace(); }finally{ if(rs!=null){ try { rs.close(); } catch (SQLException e) { e.printStackTrace(); }finally{ rs=null; } } if(ps!=null){ try { ps.close(); } catch (SQLException e) { e.printStackTrace(); }finally{ ps=null; } } if(conn!=null){ try { conn.close(); } catch (SQLException e) { e.printStackTrace(); }finally{ conn=null; } } } } }
2.c3p0
C3P0数据源：
方式1：
ComboPooledDataSource source = new ComboPooledDataSource();
source.setDriverClass("com.mysql.jdbc.Driver");
source.setJdbcUrl("jdbc:mysql:///day11");
source.setUser("root");
source.setPassword("root");
方式2：
ComboPooledDataSource source = new ComboPooledDataSource();
在类加载目录下名称为c3p0-config.xml的配置文件中配置:
<c3p0-config>
<default-config>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql:///day11</property>
<property name="user">root</property>
<property name="password">root</property>
</default-config>
</c3p0-config>
c3p0配置文件：
<?xml version="1.0" encoding="utf-8"?> <c3p0-config> <default-config> <property name="driverClass">com.mysql.jdbc.Driver</property> <property name="jdbcUrl">jdbc:mysql://localhost:3306/database01?Unicode=true&characterEncoding=utf-8</property> <property name="user">root</property> <property name="password"></property> </default-config> <named-config name="aaa"> <property name="driverClass">com.mysql.jdbc.Driver</property> <property name="jdbcUrl">jdbc:mysql://localhost:3306/database01?Unicode=true&characterEncoding=utf-8</property> <property name="user">root</property> <property name="password"></property> </named-config> </c3p0-config>
示例代码：
package com.dzq.jdbc; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import com.mchange.v2.c3p0.ComboPooledDataSource; public class C3P0Demo { public static void main(String[] args) { Connection conn=null; PreparedStatement ps=null; ResultSet rs=null; try { ComboPooledDataSource source=new ComboPooledDataSource(); /* ComboPooledDataSource source=new ComboPooledDataSource(); source.setDriverClass("com.mysql.jdbc.Driver"); source.setJdbcUrl("jdbc:mysql://localhost:3306/database01?Unicode=true&characterEncoding=utf-8"); source.setUser("root"); source.setPassword("");*/ conn=source.getConnection(); String sql="select * from account"; ps=conn.prepareStatement(sql); rs=ps.executeQuery(); while (rs.next()) { String name=rs.getString("name"); System.out.println(name); } } catch (Exception e) { e.printStackTrace(); }finally{ if(rs!=null){ try { rs.close(); } catch (SQLException e) { e.printStackTrace(); }finally{ rs=null; } } if(ps!=null){ try { ps.close(); } catch (SQLException e) { e.printStackTrace(); }finally{ ps=null; } } if(conn!=null){ try { conn.close(); } catch (SQLException e) { e.printStackTrace(); }finally{ conn=null; } } } } }
3.tomcat 数据源
tomcat内置的数据源(DBCP):
~1.如何为tomcat配置数据源
~tomcat/conf/context.xml文件中配置<Context>配置在这个位置的信息将会被所有的web应用所共享
~tomcat/conf/[engin]/[Host]/context.xml文件中可以配置<Context>标签,这里配置的信息将会被这台虚拟主机中的所有web应用所共享
~tomcat/conf/server.xml文件中的<Host>标签中配置<Context>标签,这是web应用的第一种配置方式,在这个标签中配置的信息将只对当前web应用起作用
~tomcat/conf/[engin]/[Host]/自己创建一个.xml文件,在这个文件中使用<Context>标签配置一个web应用,这是web应用第二种配置方式,在这个<Context>标签中配置的信息将只会对当前web应用起作用
~web应用还有第三种配置方式:将web应用直接放置到虚拟主机管理的目录.此时可以在web应用的META-INF文件夹下创建一个context.xml文件,在其中可以写<Context>标签进行配置,这种配置信息将只会对当前web应用起作用
<Resource name="mySource"
auth="Container"
type="javax.sql.DataSource"
username="root"
password="root"
driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql:///day11"
maxActive="8"
maxIdle="4"/>
~2.如何在程序中获取这个数据源
想要访问jndi就必须在Servlet中才能执行下列代码:
Context initCtx = new InitialContext();
Context jndi = (Context) initCtx.lookup("java:comp/env");
DataSource source = jndi.lookUp("mySource");
配置文件context.xml
<?xml version="1.0" encoding="utf-8" ?> <Context> <Resource name="mySource" auth="Container" type="javax.sql.DataSource" username="root" password="" driverClassName="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost:3306/database01?Unicode=true&characterEncoding=utf-8" maxActive="8" maxIdle="4"/> </Context>
示例代码：
package com.dzq.init; import java.io.IOException; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import javax.naming.Context; import javax.naming.InitialContext; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.sql.DataSource; @WebServlet("/DataSourceInitServlet") public class DataSourceInitServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } @Override public void init() throws ServletException { try{ Context initCtx = new InitialContext(); Context jndi = (Context) initCtx.lookup("java:comp/env"); DataSource source = (DataSource) jndi.lookup("mySource"); Connection conn = source.getConnection(); PreparedStatement ps = conn.prepareStatement("select * from account"); ResultSet rs = ps.executeQuery(); while(rs.next()){ String name = rs.getString("name"); System.out.println(name); } rs.close(); ps.close(); conn.close(); }catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } } }
