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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