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自己实现的一个简单的数据库连接池
自己突然就找到了以前学习的感觉,要不是完了这几个月英爱能找一份比现在好点的工作,说实话还是有点后悔,但是没关系,从现在开始加油还来得及。
今天首先学的是数据库连接，就想到了实现一个数据库连接池，虽然很Lower 但是还是记录下来，一步一个脚印.
首先实现方法是创建一个连接池对象,里面放一个List对象用来保存数据库连接,自己写一个类,实现Connection对象，在里面的close方法里面将连接还给连接池。
然后在从数据库连接池中获取数据的时候用removeFirst方法,移除并返回第一个对象，好的废话不多说上代码
package com.mysql;import java.sql.Connection;import java.sql.DriverManager;import java.util.ArrayList;import java.util.LinkedList;import java.util.List;public class JDBC_POOL { private static final String URL = "jdbc:mysql://localhost:3306/JDBC_TEST?useUnicode=true&characterEncoding=UTF-8"; private static final String DRIVER = "com.mysql.jdbc.Driver"; private static final String USER_NAME = "root"; private static final String PASSWORD = "dbq228367/"; /** * 用来装连接池的容器 */ public static LinkedList<myConnection> list = new LinkedList<myConnection>(); /** * 设置容器的大小 */ public static int size = 100; static{ try{ for(int i=0;i<3;i++){ Connection conn = DriverManager.getConnection(URL, USER_NAME, PASSWORD); System.out.println("创建了数据库连接 : " + conn + " : " + conn.hashCode()); myConnection mc = new myConnection(conn); list.add(mc); } }catch(Exception e){ System.out.println(e.getMessage()); e.printStackTrace(); } } public myConnection getConnection()throws Exception{ if(list.size()==0 || list.size()<0){ //连接池已经满了 throw new Exception("连接池已经没有连接对象"); }else{ System.out.println("程序获取连接对象 ： " + list.get(0).getConnection()); return list.removeFirst(); } }}然后是实现Connection接口的自定义类
package com.mysql;import java.sql.Array;import java.sql.Blob;import java.sql.CallableStatement;import java.sql.Clob;import java.sql.Connection;import java.sql.DatabaseMetaData;import java.sql.NClob;import java.sql.PreparedStatement;import java.sql.SQLClientInfoException;import java.sql.SQLException;import java.sql.SQLWarning;import java.sql.SQLXML;import java.sql.Savepoint;import java.sql.Statement;import java.sql.Struct;import java.util.Map;import java.util.Properties;public class myConnection implements Connection{ private Connection conn; public myConnection(Connection conn){ this.conn = conn; } @Override public <T> T unwrap(Class<T> iface) throws SQLException { // TODO Auto-generated method stub return conn.unwrap(iface); } @Override public boolean isWrapperFor(Class<?> iface) throws SQLException { // TODO Auto-generated method stub return conn.isWrapperFor(iface); } @Override public Statement createStatement() throws SQLException { // TODO Auto-generated method stub return conn.createStatement(); } @Override public PreparedStatement prepareStatement(String sql) throws SQLException { // TODO Auto-generated method stub return conn.prepareStatement(sql); } @Override public CallableStatement prepareCall(String sql) throws SQLException { // TODO Auto-generated method stub return conn.prepareCall(sql); } @Override public String nativeSQL(String sql) throws SQLException { // TODO Auto-generated method stub return conn.nativeSQL(sql); } @Override public void setAutoCommit(boolean autoCommit) throws SQLException { // TODO Auto-generated method stub conn.setAutoCommit(autoCommit); } @Override public boolean getAutoCommit() throws SQLException { // TODO Auto-generated method stub return conn.getAutoCommit(); } @Override public void commit() throws SQLException { // TODO Auto-generated method stub conn.commit(); } @Override public void rollback() throws SQLException { // TODO Auto-generated method stub conn.rollback(); } @Override public void close() throws SQLException { // TODO Auto-generated method stub //在这里将连接对象还给连接池 System.out.println("将连接对象还给连接池 : " + conn); JDBC_POOL.list.add(new myConnection(conn)); } @Override public boolean isClosed() throws SQLException { // TODO Auto-generated method stub return conn.isClosed(); } @Override public DatabaseMetaData getMetaData() throws SQLException { // TODO Auto-generated method stub return conn.getMetaData(); } @Override public void setReadOnly(boolean readOnly) throws SQLException { // TODO Auto-generated method stub conn.setReadOnly(readOnly); } @Override public boolean isReadOnly() throws SQLException { // TODO Auto-generated method stub return conn.isReadOnly(); } @Override public void setCatalog(String catalog) throws SQLException { // TODO Auto-generated method stub conn.setCatalog(catalog); } @Override public String getCatalog() throws SQLException { // TODO Auto-generated method stub return conn.getCatalog(); } @Override public void setTransactionIsolation(int level) throws SQLException { // TODO Auto-generated method stub conn.setTransactionIsolation(level); } @Override public int getTransactionIsolation() throws SQLException { // TODO Auto-generated method stub return conn.getTransactionIsolation(); } @Override public SQLWarning getWarnings() throws SQLException { // TODO Auto-generated method stub return conn.getWarnings(); } @Override public void clearWarnings() throws SQLException { // TODO Auto-generated method stub conn.clearWarnings(); } @Override public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException { // TODO Auto-generated method stub return conn.createStatement(resultSetType, resultSetConcurrency); } @Override public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException { // TODO Auto-generated method stub return conn.prepareStatement(sql, resultSetType,resultSetConcurrency); } @Override public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException { // TODO Auto-generated method stub return conn.prepareCall(sql, resultSetType, resultSetConcurrency, resultSetConcurrency); } @Override public Map<String, Class<?>> getTypeMap() throws SQLException { // TODO Auto-generated method stub return conn.getTypeMap(); } @Override public void setTypeMap(Map<String, Class<?>> map) throws SQLException { // TODO Auto-generated method stub conn.setTypeMap(map); } @Override public void setHoldability(int holdability) throws SQLException { // TODO Auto-generated method stub conn.setHoldability(holdability); } @Override public int getHoldability() throws SQLException { // TODO Auto-generated method stub return conn.getHoldability(); } @Override public Savepoint setSavepoint() throws SQLException { // TODO Auto-generated method stub return conn.setSavepoint(); } @Override public Savepoint setSavepoint(String name) throws SQLException { // TODO Auto-generated method stub return conn.setSavepoint(name); } @Override public void rollback(Savepoint savepoint) throws SQLException { // TODO Auto-generated method stub conn.rollback(savepoint); } @Override public void releaseSavepoint(Savepoint savepoint) throws SQLException { // TODO Auto-generated method stub conn.releaseSavepoint(savepoint); } @Override public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { // TODO Auto-generated method stub return conn.createStatement(resultSetType, resultSetConcurrency, resultSetHoldability); } @Override public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { // TODO Auto-generated method stub return conn.prepareStatement(sql, resultSetType, resultSetConcurrency,resultSetHoldability); } @Override public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException { // TODO Auto-generated method stub return conn.prepareCall( sql, resultSetType, resultSetConcurrency, resultSetHoldability); } @Override public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException { // TODO Auto-generated method stub return conn.prepareStatement( sql, autoGeneratedKeys); } @Override public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException { // TODO Auto-generated method stub return conn.prepareStatement( sql, columnIndexes); } @Override public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException { // TODO Auto-generated method stub return conn.prepareStatement( sql, columnNames); } @Override public Clob createClob() throws SQLException { // TODO Auto-generated method stub return conn.createClob(); } @Override public Blob createBlob() throws SQLException { // TODO Auto-generated method stub return conn.createBlob(); } @Override public NClob createNClob() throws SQLException { // TODO Auto-generated method stub return conn.createNClob(); } @Override public SQLXML createSQLXML() throws SQLException { // TODO Auto-generated method stub return conn.createSQLXML(); } @Override public boolean isValid(int timeout) throws SQLException { // TODO Auto-generated method stub return conn.isValid(timeout); } @Override public void setClientInfo(String name, String value) throws SQLClientInfoException { // TODO Auto-generated method stub conn.setClientInfo(name, value); } @Override public void setClientInfo(Properties properties) throws SQLClientInfoException { // TODO Auto-generated method stub conn.setClientInfo(properties); } @Override public String getClientInfo(String name) throws SQLException { // TODO Auto-generated method stub return conn.getClientInfo(name); } @Override public Properties getClientInfo() throws SQLException { // TODO Auto-generated method stub return conn.getClientInfo(); } @Override public Array createArrayOf(String typeName, Object[] elements) throws SQLException { // TODO Auto-generated method stub return conn.createArrayOf(typeName, elements); } @Override public Struct createStruct(String typeName, Object[] attributes) throws SQLException { // TODO Auto-generated method stub return conn.createStruct(typeName, attributes); } public Connection getConnection(){ return this.conn; }}注意看里面的close方法,和最后一个getConnection方法,getConnection方法是为了直观的观察数据库连接池里面对象的流转情况
然后在servlet里面调用并打印数据库连接池信息
package com.servlet;import java.io.IOException;import java.io.PrintWriter;import java.sql.Connection;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.mysql.JDBC_POOL;import com.mysql.myConnection;public class getConnection extends HttpServlet { private static final long serialVersionUID = 1806541121588301641L; public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { doPost(request,response); } public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { PrintWriter out = response.getWriter(); try{ Connection conn = new JDBC_POOL().getConnection(); out.print(conn+" : " + conn.hashCode()); }catch(Exception e){ System.out.println(e.getMessage()); e.printStackTrace(); }finally{ } }}最后我们来看看效果
还有控制台打印的信息
创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@66922804 : 1720854532创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@47124746 : 1192380230创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@26aae86e : 648734830程序获取连接对象 ： com.mysql.jdbc.JDBC4Connection@66922804
再访问一次
创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@66922804 : 1720854532创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@47124746 : 1192380230创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@26aae86e : 648734830程序获取连接对象 ： com.mysql.jdbc.JDBC4Connection@66922804程序获取连接对象 ： com.mysql.jdbc.JDBC4Connection@47124746
第三次
创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@66922804 : 1720854532创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@47124746 : 1192380230创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@26aae86e : 648734830程序获取连接对象 ： com.mysql.jdbc.JDBC4Connection@66922804程序获取连接对象 ： com.mysql.jdbc.JDBC4Connection@47124746程序获取连接对象 ： com.mysql.jdbc.JDBC4Connection@26aae86e
好的这时候三个连接对象都取完了，我们来第四次访问
创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@66922804 : 1720854532创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@47124746 : 1192380230创建了数据库连接 : com.mysql.jdbc.JDBC4Connection@26aae86e : 648734830程序获取连接对象 ： com.mysql.jdbc.JDBC4Connection@66922804程序获取连接对象 ： com.mysql.jdbc.JDBC4Connection@47124746程序获取连接对象 ： com.mysql.jdbc.JDBC4Connection@26aae86e连接池已经没有连接对象java.lang.Exception: 连接池已经没有连接对象 at com.mysql.JDBC_POOL.getConnection(JDBC_POOL.java:41) at com.servlet.getConnection.doPost(getConnection.java:26) at com.servlet.getConnection.doGet(getConnection.java:20) at javax.servlet.http.HttpServlet.service(HttpServlet.java:690) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:619)
到这里和预想的一样,在servlet中如果释放了数据库连接,则我们也可以看到连接还给连接池的信息，这里就不再赘述。
自己实现的一个简单的数据库连接池
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