连接池3：代理模式重写close方法

怼烎@ 2022-08-09 01:54 108阅读 0赞

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();
                    }
                }
            }
        }
    }