java_jdbc_基本连接池

MyDataSource实现封装连接池，MyConnection实现connection类，通过代理模式相互调用

package cn.itcast;

import java.sql.*;

public class ConnectDemo {

	public static void main(String[] args) throws Exception {
		for(int i=0;i<21;i++){
			Connection conn = JdbcUtils.getConnection();
			System.out.println(conn);
			JdbcUtils.free(null, null, conn);
		}
	}

}

package cn.itcast;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import cn.itcast.datasource.DataSourceDemo1;

public final class JdbcUtils {

	// private static String url = "jdbc:mysql://";
	// private static String user = "";
	// private static String password = "";

	private static MyDataSource mydatasource = null;

	public JdbcUtils() {
	}

	static {
		try {
			Class.forName("com.mysql.jdbc.Driver");
			mydatasource = new MyDataSource();
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			throw new ExceptionInInitializerError(e);
		}
	}

	public static Connection getConnection() throws SQLException {
		return mydatasource.getConnection();
	}

	public static void free(ResultSet rs, Statement st, Connection conn) {
		try {
			if (rs != null)
				rs.close();
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			try {
				if (st != null)
					st.close();
			} catch (SQLException e) {
				e.printStackTrace();
			} finally {
				if (conn != null)
					try {
						conn.close();
//						mydatasource.free(conn);
					} catch (Exception e) {
						e.printStackTrace();
					}
			}
		}
	}
}

package cn.itcast;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.LinkedList;

public class MyDataSource {

	private static String url = "jdbc:mysql://";
	private static String user = "";
	private static String password = "";

	// 初始化连接数
	private static int initCount = 5;
	//最大创建数
	private static int maxCount = 10;
	int currentCount = 0;

	public LinkedList<Connection> connectionsPool = new LinkedList<Connection>();

	public MyDataSource() {
		for (int i = 0; i < initCount; i++) {
			try {
				this.connectionsPool.addLast(this.createConnection());
				this.currentCount++;
			} catch (SQLException e) {
				throw new ExceptionInInitializerError(e);
			}
		}
	}

	public Connection getConnection() throws SQLException {

		synchronized (connectionsPool) {
			if (this.connectionsPool.size() > 0) {
				return this.connectionsPool.removeFirst();
			} else if (this.currentCount < maxCount) {
				this.currentCount++;
				return this.createConnection();
			} else {
				throw new SQLException("超过最大连接数量");
			}

		}
	}

	public void free(Connection conn) {
		this.connectionsPool.addLast(conn);
	}

	private Connection createConnection() throws SQLException {
		Connection realConn = DriverManager.getConnection(url, user, password);
		MyConnection myConnection = new MyConnection(realConn, this);
		return myConnection;
	}
}

package cn.itcast;

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;

import cn.itcast.datasource.DataSourceDemo1;

public class MyConnection implements Connection {
	private Connection realConnection;
	private MyDataSource dataSource;
	//连接最大使用次数
	private int maxUseCount = 10;
	//当前使用次数
	private int currentUserCount = 0;

	MyConnection(Connection connection, MyDataSource datasource) {
		this.realConnection = connection;
		this.dataSource = datasource;
	}

	@Override
	public void close() throws SQLException {
		// TODO Auto-generated method stub
		this.currentUserCount++;
		if (this.currentUserCount > this.maxUseCount)
			this.dataSource.connectionsPool.addLast(this);
		else {

			this.realConnection.close();// 真正关掉
			this.dataSource.currentCount--;
		}
	}

	@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 Statement createStatement() throws SQLException {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public PreparedStatement prepareStatement(String sql) throws SQLException {
		// TODO Auto-generated method stub
		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
		this.realConnection.commit();
	}

	@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
		this.realConnection.clearWarnings();
	}

	@Override
	public Statement createStatement(int resultSetType, int resultSetConcurrency)
			throws SQLException {
		// TODO Auto-generated method stub
		return this.realConnection.createStatement();
	}

	@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;
	}

}