连接池3：代理模式重写close方法-蒲公英云

这种代码在实际中很少会使用，因为会有现成的框架来使用。

1，新的数据源

package cn.itcast.jdbc.dataSource;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.LinkedList;
public class MyDataSource2 { 
    private static String url = "jdbc:mysql://localhost:3306/jdbc";
    private static String user = "root";
    private static String password = "123456";
    private static int initCount = 5;
    private static int maxCount = 10;
    private int currentCount = 0;
    public static void main(String[] args) {
    }
    LinkedList<Connection> connectionPool = new LinkedList<Connection>();
    public MyDataSource2() {
        try {
            for (int i = 0; i < initCount; i++) {
                this.connectionPool.addLast(this.createConnection());
                this.currentCount++;
            }
        } catch (SQLException e) {
            throw new ExceptionInInitializerError();
        }
    }
    public Connection getConnection() throws SQLException {
        synchronized (connectionPool) {
            if (this.connectionPool.size() > 0)
                return this.connectionPool.removeFirst();
            if (this.currentCount < maxCount) {
                this.currentCount++;
                return this.createConnection();
            }
            throw new SQLException("已经没有可用连接");
        }
    }
    public void free(Connection conn) {
        this.connectionPool.addLast(conn);
    }
    private Connection createConnection() throws SQLException {
        Connection realConn = DriverManager.getConnection(url, user, password);
        MyConnection myConnection = new MyConnection(realConn, this);
        return myConnection;
    }
}

2，修改close方法
实现Connection接口

package cn.itcast.jdbc.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;
public class MyConnection implements Connection { 
    private Connection realConnection;
    private MyDataSource2 dataSource;
    MyConnection(java.sql.Connection connection, MyDataSource2 dataSource) {
        realConnection = connection;
        this.dataSource = dataSource;
    }
    @Override
    public void close() throws SQLException {       //修改close方法，放回连接池而不是关闭连接
        this.dataSource.connectionPool.addLast(this);
    }
    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        return this.realConnection.unwrap(iface); // 后面的做法相同，都交给realConnection去做
    }
    @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
    }
    @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;
    }
}

3，修改工具类

package cn.itcast.jdbc;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import cn.itcast.jdbc.dataSource.MyDataSource2;
public final class JdbcUtils { 
    private static MyDataSource2 myDataSource = null;
    private JdbcUtils() {
    }
    static {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            myDataSource = new MyDataSource2();
        } catch (Exception e) {
            throw new ExceptionInInitializerError(e);
        }
    }
    public static Connection getConnection() throws SQLException {
        // return DriverManager.getConnection(url, user, password);
        return myDataSource.getConnection(); // 取连接
    }
    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();//现在close方法就是将连接放回连接池，而不是关闭连接
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                try {
                    if (conn != null)
                         conn.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }
}