JDBC自定义连接池过程详解

这篇文章主要介绍了JDBC自定义连接池过程详解,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下

开发中，"获得连接"和"释放资源"是非常消耗系统资源的，为了解决此类性能问题可以采用连接池技术来共享连接Connection。

1、概述

用池来管理Connection,这样可以重复使用Connection.这样我们就不用创建Connection,用池来管理Connection对象，当使用完Connection对象后，将Connection对象归还给池，这样后续还可以从池中获取Connection对象，可以重新再利用这个连接对象啦。

java为数据库连接池提供了公共接口：javax.sql.DataSource,各个厂商需要让自己的连接池实现这个接口。
常见的连接池：DBCP,C3P0

2、自定义连接池

编写自定义连接池

1、创建连接池并实现接口javax.sql.DataSource，并使用接口中的getConnection()方法

2、提供一个集合，用于存放连接，可以采用LinkedList

3、后面程序如果需要，可以调用实现类getConnection(),并从list中获取链接。为保证当前连接只能提供给一个线程使用，所以我们需要将连接先从连接池中移除

4、当用户用完连接后，将连接归还到连接池中

3、自定义连接池采用装饰者设计模式

public class ConnectionPool implements Connection {

  private Connection connection;
  private LinkedList<Connection> pool;

  public ConnectionPool(Connection connection, LinkedList<Connection> pool){
    this.connection=connection;
    this.pool=pool;
  }

  @Override
  public PreparedStatement prepareStatement(String sql) throws SQLException {
    return connection.prepareStatement(sql);
  }

  @Override
  public void close() throws SQLException {
    pool.add(connection);

  }
  @Override
  public Statement createStatement() throws SQLException {
    return null;
  }

  @Override
  public CallableStatement prepareCall(String sql) throws SQLException {
    return null;
  }

  @Override
  public String nativeSQL(String sql) throws SQLException {
    return null;
  }

  @Override
  public void setAutoCommit(boolean autoCommit) throws SQLException {

  }

  @Override
  public boolean getAutoCommit() throws SQLException {
    return false;
  }

  @Override
  public void commit() throws SQLException {

  }

  @Override
  public void rollback() throws SQLException {

  }

  @Override
  public boolean isClosed() throws SQLException {
    return false;
  }

  @Override
  public DatabaseMetaData getMetaData() throws SQLException {
    return null;
  }

  @Override
  public void setReadOnly(boolean readOnly) throws SQLException {

  }

  @Override
  public boolean isReadOnly() throws SQLException {
    return false;
  }

  @Override
  public void setCatalog(String catalog) throws SQLException {

  }

  @Override
  public String getCatalog() throws SQLException {
    return null;
  }

  @Override
  public void setTransactionIsolation(int level) throws SQLException {

  }

  @Override
  public int getTransactionIsolation() throws SQLException {
    return 0;
  }

  @Override
  public SQLWarning getWarnings() throws SQLException {
    return null;
  }

  @Override
  public void clearWarnings() throws SQLException {

  }

  @Override
  public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
    return null;
  }

  @Override
  public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
    return null;
  }

  @Override
  public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
    return null;
  }

  @Override
  public Map<String, Class<?>> getTypeMap() throws SQLException {
    return null;
  }

  @Override
  public void setTypeMap(Map<String, Class<?>> map) throws SQLException {

  }

  @Override
  public void setHoldability(int holdability) throws SQLException {

  }

  @Override
  public int getHoldability() throws SQLException {
    return 0;
  }

  @Override
  public Savepoint setSavepoint() throws SQLException {
    return null;
  }

  @Override
  public Savepoint setSavepoint(String name) throws SQLException {
    return null;
  }

  @Override
  public void rollback(Savepoint savepoint) throws SQLException {

  }

  @Override
  public void releaseSavepoint(Savepoint savepoint) throws SQLException {

  }

  @Override
  public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
    return null;
  }

  @Override
  public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
    return null;
  }

  @Override
  public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
    return null;
  }

  @Override
  public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
    return null;
  }

  @Override
  public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
    return null;
  }

  @Override
  public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
    return null;
  }

  @Override
  public Clob createClob() throws SQLException {
    return null;
  }

  @Override
  public Blob createBlob() throws SQLException {
    return null;
  }

  @Override
  public NClob createNClob() throws SQLException {
    return null;
  }

  @Override
  public SQLXML createSQLXML() throws SQLException {
    return null;
  }

  @Override
  public boolean isValid(int timeout) throws SQLException {
    return false;
  }

  @Override
  public void setClientInfo(String name, String value) throws SQLClientInfoException {

  }

  @Override
  public void setClientInfo(Properties properties) throws SQLClientInfoException {

  }

  @Override
  public String getClientInfo(String name) throws SQLException {
    return null;
  }

  @Override
  public Properties getClientInfo() throws SQLException {
    return null;
  }

  @Override
  public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
    return null;
  }

  @Override
  public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
    return null;
  }

  @Override
  public void setSchema(String schema) throws SQLException {

  }

  @Override
  public String getSchema() throws SQLException {
    return null;
  }

  @Override
  public void abort(Executor executor) throws SQLException {

  }

  @Override
  public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {

  }

  @Override
  public int getNetworkTimeout() throws SQLException {
    return 0;
  }

  @Override
  public <T> T unwrap(Class<T> iface) throws SQLException {
    return null;
  }

  @Override
  public boolean isWrapperFor(Class<?> iface) throws SQLException {
    return false;
  }
}

DataSourcePool

public class DataSourcePool implements DataSource {
  //1.创建1个容器用于存储Connection对象
  private static LinkedList<Connection> pool = new LinkedList<Connection>();

  //2.创建5个连接放到容器中去
  static{
    for (int i = 0; i < 5; i++) {
      Connection conn = JDBCUtils.getConnection();
      //放入池子中connection对象已经经过改造了
      ConnectionPool connectionPool = new ConnectionPool(conn, pool);
      pool.add(connectionPool);
    }
  }

  /**
   * 重写获取连接的方法
   */
  @Override
  public Connection getConnection() throws SQLException {
    Connection conn = null;
    //3.使用前先判断
    if(pool.size()==0){
      //4.池子里面没有，我们再创建一些
      for (int i = 0; i < 5; i++) {
        conn = JDBCUtils.getConnection();
        //放入池子中connection对象已经经过改造了
        ConnectionPool connectionPool = new ConnectionPool(conn, pool);
        pool.add(connectionPool);
      }
    }
    //5.从池子里面获取一个连接对象Connection
    conn = pool.remove(0);
    return conn;
  }

  @Override
  public Connection getConnection(String username, String password) throws SQLException {
    return null;
  }

  @Override
  public <T> T unwrap(Class<T> iface) throws SQLException {
    return null;
  }

  @Override
  public boolean isWrapperFor(Class<?> iface) throws SQLException {
    return false;
  }

  @Override
  public PrintWriter getLogWriter() throws SQLException {
    return null;
  }

  @Override
  public void setLogWriter(PrintWriter out) throws SQLException {

  }

  @Override
  public void setLoginTimeout(int seconds) throws SQLException {

  }

  @Override
  public int getLoginTimeout() throws SQLException {
    return 0;
  }

  @Override
  public Logger getParentLogger() throws SQLFeatureNotSupportedException {
    return null;
  }
}

测试代码如下

 @Test
  public void test1(){
    Connection conn = null;
    PreparedStatement pstmt = null;
    // 1.创建自定义连接池对象
    DataSource dataSource = new DataSourcePool();
    try {
      // 2.从池子中获取连接
      conn = dataSource.getConnection();
      String sql = "insert into USER values(?,?)";
      //3.必须在自定义的connection类中重写prepareStatement(sql)方法
      pstmt = conn.prepareStatement(sql);
      pstmt.setString(1, "李四");
      pstmt.setString(2, "1234");
      int rows = pstmt.executeUpdate();
      System.out.println("rows:"+rows);
    } catch (Exception e) {
      throw new RuntimeException(e);
    } finally {
      JDBCUtils.relase(conn, pstmt, null);
    }
  }

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