c3p0数据库连接池实例

c3p0下载地址：http://download.csdn.net/detail/huhui_bj/6944595

这篇文章介绍的是，在普通Java Web工程中或者普通Java工程中使用c3p0数据库连接池的实例，c3p0的jar文件包括3个。下面这个实例工程中，主要包括三个重要的文件：
C3P0ConnentionProvider.java       初始化c3p0数据库连接池

SQLHelper.java         通过数据库连接池，提供对数据库的增删改查功能

c3p0.properties  c3p0的配置文件

工程文件的截图如下：

c3p0.properties文件内容如下：

#jdbc基本信息driverClass=oracle.jdbc.driver.OracleDriverjdbcUrl=jdbc:oracle:thin:@127.0.0.1:1521:orcluser=scottpassword=tigger#c3p0连接池信息c3p0.minPoolSize=3c3p0.maxPoolSize=25#当连接池中的连接耗尽的时候c3p0一次同时获取的连接数c3p0.acquireIncrement=3#定义在从数据库获取新连接失败后重复尝试的次数c3p0.acquireRetryAttempts=60#两次连接中间隔时间，单位毫秒c3p0.acquireRetryDelay=1000#连接关闭时默认将所有未提交的操作回滚 c3p0.autoCommitOnClose=false#当连接池用完时客户端调用getConnection()后等待获取新连接的时间，超时后将抛出SQLException,如设为0则无限c3p0.checkoutTimeout=3000#每120秒检查所有连接池中的空闲连接。Default: 0c3p0.idleConnectionTestPeriod=120#最大空闲时间,60秒内未使用则连接被丢弃。若为0则永不丢弃。Default: 0  c3p0.maxIdleTime=600#如果设为true那么在取得连接的同时将校验连接的有效性。Default: false  c3p0.testConnectionOnCheckin=false#如果maxStatements与maxStatementsPerConnection均为0，则缓存被关闭。Default: 0c3p0.maxStatements=8#maxStatementsPerConnection定义了连接池内单个连接所拥有的最大缓存statements数。Default: 0c3p0.maxStatementsPerConnection=5

C3P0ConnentionProvider.java文件内容如下：

package com.hh.db;import java.io.FileInputStream;import java.sql.Connection;import java.sql.SQLException;import java.util.Properties;import javax.sql.DataSource;import com.mchange.v2.c3p0.DataSources;/** * c3p0连接池管理类 */public class C3P0ConnentionProvider {private static final String JDBC_DRIVER = "driverClass";private static final String JDBC_URL = "jdbcUrl";private static DataSource ds;/** * 初始化连接池代码块 */static {initDBSource();}/** * 初始化c3p0连接池 */private static final void initDBSource() {Properties c3p0Pro = new Properties();try {// 加载配置文件String path = C3P0ConnentionProvider.class.getResource("/").getPath();String websiteURL = (path.replace("/build/classes", "").replace("%20"," ").replace("classes/", "") + "c3p0.properties").replaceFirst("/", "");FileInputStream in = new FileInputStream(websiteURL);c3p0Pro.load(in);} catch (Exception e) {e.printStackTrace();}String drverClass = c3p0Pro.getProperty(JDBC_DRIVER);if (drverClass != null) {try {// 加载驱动类Class.forName(drverClass);} catch (ClassNotFoundException e) {e.printStackTrace();}}Properties jdbcpropes = new Properties();Properties c3propes = new Properties();for (Object key : c3p0Pro.keySet()) {String skey = (String) key;if (skey.startsWith("c3p0.")) {c3propes.put(skey, c3p0Pro.getProperty(skey));} else {jdbcpropes.put(skey, c3p0Pro.getProperty(skey));}}try {// 建立连接池DataSource unPooled = DataSources.unpooledDataSource(c3p0Pro.getProperty(JDBC_URL), jdbcpropes);ds = DataSources.pooledDataSource(unPooled, c3propes);} catch (SQLException e) {e.printStackTrace();}}/** * 获取数据库连接对象 *  * @return 数据连接对象 * @throws SQLException */public static synchronized Connection getConnection() throws SQLException {final Connection conn = ds.getConnection();conn.setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED);return conn;}}

SQLHelper.java文件内容如下：

/** * 功能：提供统一的查询、修改和插入方法 */package com.hh.db;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.ResultSetMetaData;import java.util.ArrayList;import java.util.List;public class SQLHelper {private Connection conn = null;private PreparedStatement ps = null;private ResultSet rs = null;/** * 数据查询 * @param sql语句 * @return 返回结果集List<Object> */public List<Object> query(String sql) {if(sql.equals("") || sql == null){return null;}List<Object> list = new ArrayList<Object>();try {conn = C3P0ConnentionProvider.getConnection();ps = conn.prepareStatement(sql);rs = ps.executeQuery();ResultSetMetaData rsmd = rs.getMetaData();// 可以得到有多少列int columnNum = rsmd.getColumnCount();// 将数据封装到list中while (rs.next()) {Object[] objects = new Object[columnNum];for (int i = 0; i < objects.length; i++) {objects[i] = rs.getObject(i + 1);}list.add(objects);}} catch (Exception e) {// TODO: handle exceptione.printStackTrace();}return list;}/** * 插入、修改数据操作 * @param sql语句 * @return boolean 成功返回true，失败返回false */public boolean update(String sql) {boolean b = false;if(sql.equals("") || sql == null){return b;}try {conn = C3P0ConnentionProvider.getConnection();ps = conn.prepareStatement(sql);int i = ps.executeUpdate();if (i == 1) {b = true;}} catch (Exception e) {// TODO: handle exceptione.printStackTrace();}return b;}}

至于Demo.java文件，可提供参考的内容如下：

/** * SQLHelper的测试类 *  */package com.hh.db;import java.util.ArrayList;import java.util.List;public class Demo {private SQLHelper sqlHelper = new SQLHelper();/** * 测试query *//*public void testQuery(){String sql = "select * from crh2_station where id = 1";List list = sqlHelper.query(sql);List<Crh2Station> crh2StationList = new ArrayList<Crh2Station>();//对查询结果进行封装for (int i = 0; i < list.size(); i++) {Object object[] = (Object[]) list.get(i);Crh2Station crh2Station = new Crh2Station();crh2Station.setId(Integer.parseInt(object[0].toString()));crh2Station.setSlopeId(Integer.parseInt(object[1].toString()));crh2Station.setSlope(Double.parseDouble(object[2].toString()));crh2Station.setLength(Double.parseDouble(object[3].toString()));crh2Station.setEnd(Double.parseDouble(object[4].toString()));crh2Station.setHeight(Double.parseDouble(object[5].toString()));crh2StationList.add(crh2Station);}return crh2StationList;}*//** * 测试insert、update、delete *//*public void testInsertOrUpdate(){String sql = "delete from crh2_station where id = 1";boolean b = sqlHelper.update(sql);if(b){//b为true则操作成功System.out.println("操作成功");}else{//b为false则操作失败System.out.println("操作失败");}}*/}

参考资料：http://blog.csdn.net/wushangjimo/article/details/12654491