package star.july.dataSource;
import java.sql.Connection;
import java.sql.SQLException;
public class MyDao {
public static void main(String[] args) throws SQLException {
//创建连接池程序
MyDataSource ds = new MyDataSource();
for(int i =1; i<=11;i++){
//从连接池程序获取对象
Connection conn = ds.getConnection();
System.out.println(conn);
//模拟第三个用户释放了连接
if(i ==1){
//使用回Connection.close()方法释放链接
//问题：close（）方法原来并不是连接放回连接池，而是关闭连接
//解决方法：让close（）能够实现放回连接池的功能
//即用代理方法包装类
conn.close();
}
}
}
}
自定义连接池:
package star.july.dataSource;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.LinkedList;
import java.util.logging.Logger;
import javax.sql.DataSource;
//自定义连接池
public class MyDataSource implements DataSource{
private static String driverClass = "com.mysql.jdbc.Driver";
private static String url = "jdbc:mysql://localhost:3306/day18";
private static String user = "root";
private static String password = "root";
//设计一个集合用于存放连接对象
private static LinkedList<Connection> pool = new LinkedList<Connection>();
//初始化连接数
private int initConn = 5;
//数据库能够承受的最大连接数
private int maxConn = 10;
//用于记录连接池一共提供了多少个连接数
private int curConn = 0;
//当初始化连接池程序的时候，就已经初始化了若干个对象
public MyDataSource(){
//创建5个连接对象，放入集合中
for(int i =1 ; i <= initConn; i ++){
curConn++;
pool.add(createConnection());
}
}
static{
//注册驱动
try{
Class.forName(driverClass);
}catch(ClassNotFoundException e){
e.printStackTrace();
}
}
//创建一个连接对象的方法
public Connection createConnection(){
try{
//被代理类对象
Connection conn = DriverManager.getConnection(url,user,password);
//创建代理类对象
MyConnectionProxy proxy = new MyConnectionProxy(conn,this);
return proxy;
}catch(SQLException e){
e.printStackTrace();
throw new RuntimeException();
}
}
//这个方法提供给外部程序获取连接对象的
@Override
public Connection getConnection() throws SQLException {
//情况1:并发连接数小于等于初始化连接数的时候，直接初始化连接取出即可
if(pool.size()>0){
Connection conn = pool.removeLast();
return conn;
}
//情况2：并发连接数大于初始连接数且小于最大连接数，重新再创建新的链接给用户
if(curConn<maxConn){
curConn++;
return createConnection();
}
//情况3：并发连接数大于最大连接数时，不能再提供连接数
throw new RuntimeException();
}
//释放连接，把连接放回连接池程序
public void releaseConnection(Connection conn){
pool.addLast(conn);
}
@Override
public PrintWriter getLogWriter() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void setLogWriter(PrintWriter out) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void setLoginTimeout(int seconds) throws SQLException {
// TODO Auto-generated method stub
}
@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 <T> T unwrap(Class<T> iface) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public Connection getConnection(String username, String password)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
}
连接对象的代理类
package star.july.dataSource;
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;
import java.util.concurrent.Executor;
/**
* 连接对象的代理类
*/
public class MyConnectionProxy implements Connection{
private Connection realConn;
private MyDataSource ds;
//接收被代理类对象（JDBC4Connection）
public MyConnectionProxy(Connection conn,MyDataSource ds){
this.realConn = conn;
this.ds = ds;
}
@Override
public void close() throws SQLException {
//改写：把连接放回连接池
//调用连接池释放连接的方法
ds.releaseConnection(realConn);
}
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
return realConn.unwrap(iface);
}
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
return realConn.isWrapperFor(iface);
}
@Override
public Statement createStatement() throws SQLException {
return realConn.createStatement();
}
@Override
public PreparedStatement prepareStatement(String sql) throws SQLException {
return null;
}
@Override
public CallableStatement prepareCall(String sql) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public String nativeSQL(String sql) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void setAutoCommit(boolean autoCommit) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public boolean getAutoCommit() throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public void commit() throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void rollback() throws SQLException {
// TODO Auto-generated method stub
}
@Override
public boolean isClosed() throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public DatabaseMetaData getMetaData() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void setReadOnly(boolean readOnly) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public boolean isReadOnly() throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public void setCatalog(String catalog) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public String getCatalog() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void setTransactionIsolation(int level) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public int getTransactionIsolation() throws SQLException {
// TODO Auto-generated method stub
return 0;
}
@Override
public SQLWarning getWarnings() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void clearWarnings() throws SQLException {
// TODO Auto-generated method stub
}
@Override
public Statement createStatement(int resultSetType, int resultSetConcurrency)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PreparedStatement prepareStatement(String sql, int resultSetType,
int resultSetConcurrency) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public CallableStatement prepareCall(String sql, int resultSetType,
int resultSetConcurrency) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Map<String, Class<?>> getTypeMap() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void setTypeMap(Map<String, Class<?>> map) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void setHoldability(int holdability) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public int getHoldability() throws SQLException {
// TODO Auto-generated method stub
return 0;
}
@Override
public Savepoint setSavepoint() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Savepoint setSavepoint(String name) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void rollback(Savepoint savepoint) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void releaseSavepoint(Savepoint savepoint) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public Statement createStatement(int resultSetType,
int resultSetConcurrency, int resultSetHoldability)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PreparedStatement prepareStatement(String sql, int resultSetType,
int resultSetConcurrency, int resultSetHoldability)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public CallableStatement prepareCall(String sql, int resultSetType,
int resultSetConcurrency, int resultSetHoldability)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PreparedStatement prepareStatement(String sql, int[] columnIndexes)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public PreparedStatement prepareStatement(String sql, String[] columnNames)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Clob createClob() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Blob createBlob() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public NClob createNClob() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public SQLXML createSQLXML() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public boolean isValid(int timeout) throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public void setClientInfo(String name, String value)
throws SQLClientInfoException {
// TODO Auto-generated method stub
}
@Override
public void setClientInfo(Properties properties)
throws SQLClientInfoException {
// TODO Auto-generated method stub
}
@Override
public String getClientInfo(String name) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Properties getClientInfo() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Array createArrayOf(String typeName, Object[] elements)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public Struct createStruct(String typeName, Object[] attributes)
throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void setSchema(String schema) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public String getSchema() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void abort(Executor executor) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void setNetworkTimeout(Executor executor, int milliseconds)
throws SQLException {
// TODO Auto-generated method stub
}
@Override
public int getNetworkTimeout() throws SQLException {
// TODO Auto-generated method stub
return 0;
}
}