3中建立数据库连接池dbcp和c3p0和tomcat数据池

DBCP数据源：需要

•Commons-dbcp.jar：连接池的实现
•Commons-pool.jar：连接池实现的依赖库
dbcpconfig.properties（这个在src同目录下--模板）

#连接设置
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/jdbc
username=root
password=

#<!-- 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

#JDBC驱动建立连接时附带的连接属性属性的格式必须为这样：[属性名=property;]
#注意："user" 与 "password" 两个属性会被明确地传递，因此这里不需要包含他们。
connectionProperties=useUnicode=true;characterEncoding=gbk

#指定由连接池所创建的连接的自动提交（auto-commit）状态。
defaultAutoCommit=true

#driver default 指定由连接池所创建的连接的只读（read-only）状态。
#如果没有设置该值，则“setReadOnly”方法将不被调用。（某些驱动并不支持只读模式，如：Informix）
defaultReadOnly=

#driver default 指定由连接池所创建的连接的事务级别（TransactionIsolation）。
#可用值为下列之一：（详情可见javadoc。）NONE,READ_UNCOMMITTED, READ_COMMITTED, REPEATABLE_READ, SERIALIZABLE
defaultTransactionIsolation=READ_UNCOMMITTED

JdbcUtils_DBCP.java

package cn.lcp.utils;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

import javax.sql.DataSource;

import org.apache.commons.dbcp.BasicDataSourceFactory;

public class JdbcUtils_DBCP {

private static DataSource ds = null;
static{
try{
InputStream in = JdbcUtils_DBCP.class.getClassLoader().getResourceAsStream("dbcpconfig.properties");
Properties prop = new Properties();
prop.load(in);

BasicDataSourceFactory factory = new BasicDataSourceFactory();

ds = factory.createDataSource(prop);
System.out.println(ds);
}catch (Exception e) {
throw new ExceptionInInitializerError(e);
}
}

public static Connection getConnection() throws SQLException{

return ds.getConnection();
}

public static void release(Connection conn,Statement st,ResultSet rs){

if(rs!=null){
try{
rs.close();
}catch (Exception e) {
e.printStackTrace();
}
rs = null;

}
if(st!=null){
try{
st.close();
}catch (Exception e) {
e.printStackTrace();
}
}

if(conn!=null){
try{
conn.close();
}catch (Exception e) {
e.printStackTrace();
}
}
}

}

demo.java

package cn.lcp.demo;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Savepoint;

import cn.lcp.utils.JdbcUtils_DBCP;

//模拟转账
public class demo {

public static void main(String[] args) {
Connection conn = null;
PreparedStatement st = null;
ResultSet rs = null;

Savepoint sp = null;
try {
conn = JdbcUtils_DBCP.getConnection();
// 执行多条sql语句，开启事务
conn.setAutoCommit(false); // start transaction

String sql1 = "update account set money=money-100 where name='aaa'";
// 预编译sql语句
st = conn.prepareStatement(sql1);
st.executeUpdate();

//设置事务回滚点
sp = conn.setSavepoint();

String sql2 = "update account set money=money+100 where name='bbb'";
st = conn.prepareStatement(sql2);
st.executeUpdate();

//int i = 10 / 0;  //这里出现异常，到catch里面执行回滚

String sql3 = "update account set money=money+100 where name='ccc'";
st = conn.prepareStatement(sql3);
st.executeUpdate();

//提交事务
conn.commit();
System.out.println("成功！！！"); // log4j

} catch (Exception e) {
e.printStackTrace();
} finally {
JdbcUtils_DBCP.release(conn, st, rs);
}
}
}

加入dbcp链接池
1.导入jar包
commons-dbcp-1.2.2.jar commons-pool.jar

2、在类目录下加入dbcp的配置文件：dbcpconfig.properties

3、在jdbcUtils的静态代码块中创建池

private static DataSource ds = null;
static{
　　try{
　　　　InputStream in = JdbcUtils_DBCP.class.getClassLoader().getResourceAsStream("dbcpconfig.properties");
　　　　Properties prop = new Properties();
　　　　prop.load(in);

　　BasicDataSourceFactory factory = new BasicDataSourceFactory();

　　ds = factory.createDataSource(prop);
　　System.out.println(ds);
　　}catch (Exception e) {
　　　　throw new ExceptionInInitializerError(e);
　　}
}

使用DBCP示例代码：

static{
InputStream in = JdbcUtil.class.getClassLoader().
getResourceAsStream("dbcpconfig.properties");
Properties prop = new Properties();
prop.load(in);

BasicDataSourceFactory factory = new BasicDataSourceFactory();
dataSource = factory.createDataSource(prop);
}

C3P0 数据源

需要c3p0-pre.jar和mchange-commons.jar两个包。（这个xml在src同目录下）

c3p0-config.xml(可以当成模板)

<?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/day16</property>
<property name="user">root</property>
<property name="password">root</property>

<property name="acquireIncrement">5</property>
<property name="initialPoolSize">10</property>
<property name="minPoolSize">5</property>
<property name="maxPoolSize">20</property>
</default-config>
-->
<named-config name="mysql">
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql://localhost:3306/day16</property>
<property name="user">root</property>
<property name="password">lcp8090</property>

<property name="acquireIncrement">5</property>
<property name="initialPoolSize">10</property>
<property name="minPoolSize">5</property>
<property name="maxPoolSize">20</property>
</named-config>

<!--
<named-config name="oracle">
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql://localhost:3306/day16</property>
<property name="user">root</property>
<property name="password">root</property>

<property name="acquireIncrement">5</property>
<property name="initialPoolSize">10</property>
<property name="minPoolSize">5</property>
<property name="maxPoolSize">20</property>
</named-config>
-->
</c3p0-config>

JdbcUtils-C3P0.java

package cn.lcp.utils;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

import javax.sql.DataSource;

import org.apache.commons.dbcp.BasicDataSourceFactory;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class JdbcUtils_C3P0 {

private static ComboPooledDataSource ds = null;
static{
try{
ds = new ComboPooledDataSource("lcp");

}catch (Exception e) {
throw new ExceptionInInitializerError(e);
}
}

public static Connection getConnection() throws SQLException{

return ds.getConnection();
}

public static void release(Connection conn,Statement st,ResultSet rs){

if(rs!=null){
try{
rs.close();
}catch (Exception e) {
e.printStackTrace();
}
rs = null;

}
if(st!=null){
try{
st.close();
}catch (Exception e) {
e.printStackTrace();
}

}

if(conn!=null){
try{
conn.close();
}catch (Exception e) {
e.printStackTrace();
}
}
}
}

demo.java

package cn.lcp.demo;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Savepoint;

import cn.lcp.utils.JdbcUtils_C3P0;
import cn.lcp.utils.JdbcUtils_DBCP;

//模拟转账
public class demo {

public static void main(String[] args) {
Connection conn = null;
PreparedStatement st = null;
ResultSet rs = null;

Savepoint sp = null;
try {
conn = JdbcUtils_C3P0.getConnection();
// 执行多条sql语句，开启事务
conn.setAutoCommit(false); // start transaction

String sql1 = "update account set money=money-100 where name='aaa'";
// 预编译sql语句
st = conn.prepareStatement(sql1);
st.executeUpdate();

//设置事务回滚点
sp = conn.setSavepoint();

String sql2 = "update account set money=money+100 where name='bbb'";
st = conn.prepareStatement(sql2);
st.executeUpdate();

//int i = 10 / 0;  //这里出现异常，到catch里面执行回滚

String sql3 = "update account set money=money+100 where name='ccc'";
st = conn.prepareStatement(sql3);
st.executeUpdate();

//提交事务
conn.commit();

System.out.println("成功！！！"); // log4j

} catch (Exception e) {
e.printStackTrace();
} finally {
JdbcUtils_C3P0.release(conn, st, rs);
}
}
}

tomcat连接池：tomcat在运行时只会找自己的lib下的驱动，所以要把数据库连接驱动放到tomcat的lib文件夹下面。

context-xml,在WEB-INF目录下。(模板)

<Context>
<Resource name="jdbc/EmployeeDB"
auth="Container"
type="javax.sql.DataSource"

username="root"
password="lcp8090"
driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/day16"
maxActive="8"
maxIdle="4"/>
</Context>

ServletDemo.java

package cn.lcp.web.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import cn.lcp.dao.BaseDao;

public class ServletDemo1 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

BaseDao dao = new BaseDao();
dao.add();

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

doGet(request, response);
}

}

BaseDao.java

package cn.lcp.dao;

import java.sql.Connection;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.sql.DataSource;

public class BaseDao {

public void add(){
try{
Context initCtx = new InitialContext();  //初始化jndi
Context envCtx = (Context) initCtx.lookup("java:comp/env");  //得到jndi容器
DataSource ds = (DataSource) envCtx.lookup("jdbc/EmployeeDB");  //从容器中检索链接池

Connection conn = ds.getConnection();
System.out.println(conn);
}catch (Exception e) {
e.printStackTrace();
}
}
}