This is the same as that of the enhanced Connection class [override the close method] to retrieve connections from the Connection pool.

Packagetk. dong. connection. util; importjava. io. IOException; importjava. io. inputStream; importjava. io. printWriter; importjava. SQL. array; importjava. SQL. blob; importjava. SQL. callableStatement; importjava. SQL. clob; importjava. SQL. connection; I

Package tk. dong. connection. util; import java. io. IOException; import java. io. inputStream; import java. io. printWriter; import java. SQL. array; import java. SQL. blob; import java. SQL. callableStatement; import java. SQL. clob; import java. SQL. connection; I

Package tk. dong. connection. util; import java. io. IOException; import java. io. inputStream; import java. io. printWriter; 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. driverManager; import java. SQL. NClob; import java. SQL. preparedStatement; import java. SQL. SQLClientInfoException; import java. SQL. SQLException; import java. SQL. SQLFeatureNotSupportedException; import java. SQL. SQLWarning; import java. SQL. SQLXML; import java. SQL. savepoint; import java. SQL. statement; import java. SQL. struct; import java. util. using list; import java. util. map; import java. util. properties; import java. util. concurrent. executor; import java. util. logging. logger; import javax. SQL. dataSource; // This is the same as the enhanced Connection class [override the close method], which removes the Connection from the Connection pool and places the Connection back to the public class JdbcPool implements DataSource {// creates the Connection pool, linkList and private static upload list are used.
 
  
Connections = new external list
  
   
(); // Create a block through static initialization. When the program is initialized, static {// will be triggered to read the configuration file connected to the database into the stream. InputStream inStream = JdbcPool. class. getClassLoader (). getResourceAsStream ("jdbc. properties "); Properties properties = new Properties (); try {properties. load (inStream); // get the driver used to connect to the database (obtain the Driver Based on the attribute in the property file) Class. forName (properties. getProperty ("driverClassName"); for (int I = 0; I <10; I ++) {// obtain the conn Connection object Connection conn = DriverManager. getConnection (properties. getProperty ("url"), properties. getProperty ("user"), properties. getProperty ("pass"); // This is the operation performed when the connection pool is loaded. Rewrite the close in the connection to MyConnection myConnection = new MyConnection (conn, connections ); // Save the processed connection object to the connection pool connections. add (myConnection); System. out. println ("the connection pool has been added:" + connections. size () + ":::::::::::: link object") ;}} catch (IOException e) {// TODO Auto-generated catch blocke. printStackTrace ();} catch (ClassNotFoundException e) {// TODO Auto-generated catch blocke. printStackTrace ();} catch (SQLException e) {// TODO Auto-generated catch blocke. printStackTrace () ;}}// these two methods are used to obtain the Connection from the Connection pool @ Overridepublic Connection getConnection () throws SQLException {// The Connection object Connection conn = null; if (connections. size ()> 0) {// retrieve the first object in the linked list and assign the value to the temporary connection object conn = connections. removeFirst (); System. out. println ("another connection object is taken away: Connection Pool and" + connections. size () + "Connection objects");} return conn ;}@ Overridepublic Connection getConnection (String username, String password) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic PrintWriter getLogWriter () throws SQLException {// TODO Auto-generated method stubreturn null ;} @ Overridepublic void setLogWriter (PrintWriter out) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic void setLoginTimeout (int seconds) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic int getLoginTimeout () throws SQLException {// TODO Auto-generated method stubreturn 0 ;}@ Overridepublic Logger getParentLogger () throws SQLFeatureNotSupportedException {// TODO Auto-generated method stubreturn null;} @ Overridepublic
   
    
T unwrap (Class
    
     
Iface) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic boolean isWrapperFor (Class
     Iface) throws SQLException {// TODO Auto-generated method stubreturn false;} // enhanced Connection pair class // decorator mode // 1. first, let's take a look at the interface or parent class that needs to be inherited by the enhancement object, and write a class to inherit these interfaces or parent classes. Class MyConnection implements Connection {// 2. Define a variable in the class. The variable type is the type of the object to be enhanced. // Used to receive the private answer list of the Connection Pool
     
      
Connections; // used to receive the Connection object private Connection conn; // The constructor is public MyConnection (Connection conn, LinkedList
      
        Connections) {this. conn = conn; this. connections = connections;} // I only use this method, so I only write this method @ Overridepublic void close () throws SQLException {// Add unused connections to the connection pool connections again. add (conn); System. out. println ("A connection object is used up and the connection pool has been returned. Now there is ===" + connections in the connection pool. size ();} // The following method is not used, so no content is written @ Overridepublic
       
         T unwrap (Class
        
          Iface) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic boolean isWrapperFor (Class
         Iface) throws SQLException {// TODO Auto-generated method stubreturn false;} @ Overridepublic Statement createStatement () throws SQLException {// TODO Auto-generated method stubreturn null ;} @ Overridepublic PreparedStatement prepareStatement (String SQL) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic CallableStatement prepareCall (String SQL) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic String nativeSQL (String SQL) throws SQLException {// TODO Auto-generated method stubreturn null ;} @ Overridepublic void setAutoCommit (boolean autoCommit) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic boolean getAutoCommit () throws SQLException {// TODO Auto-generated method stubreturn false ;} @ Overridepublic void commit () throws SQLException {// TODO Auto-generated method stub} @ Overridepublic void rollback () throws SQLException {// TODO Auto-generated method stub} @ Overridepublic boolean isClosed () throws SQLException {// TODO Auto-generated method stubreturn false;} @ Overridepublic DatabaseMetaData getMetaData () throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic void setReadOnly (boolean readOnly) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic boolean isReadOnly () throws SQLException {// TODO Auto-generated method stubreturn false;} @ Overridepublic void setCatalog (String catalog) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic String getCatalog (alog () throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic void evaluate (int level) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic int getTransactionIsolation () throws SQLException {// TODO Auto-generated method stubreturn 0;} @ Overridepublic SQLWarning handle () throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic void clearWarnings () throws SQLException {// TODO Auto-generated method stub} @ Overridepublic Statement createStatement (int resultSetType, int resultSetConcurrency) throws SQLException {// TODO Auto-generated method stubreturn null ;} @ Overridepublic PreparedStatement partition (String SQL, int resultSetType, int partition) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic CallableStatement prepareCall (String SQL, int resultSetType, int resultSetConcurrency) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic Map
         
           > GetTypeMap () throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic void setTypeMap (Map
          
            > Map) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic void setHoldability (int holdability) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic int getHoldability () throws SQLException {// TODO Auto-generated method stubreturn 0;} @ Overridepublic Savepoint setSavepoint () throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic Savepoint setSavepoint (String name) throws SQLException {// TODO Auto-generated method stubreturn null ;} @ Overridepublic void rollback (Savepoint savepoint) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic void releaseSavepoint (Savepoint savepoint) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic Statement createStatement (int resultSetType, int limit, int resultSetHoldability) throws SQLException {// TODO Auto-generated method stubreturn null ;} @ Overridepublic PreparedStatement construct (String SQL, int resultSetType, int limit, int resultSetHoldability) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic CallableStatement prepareCall (String, int resultSetType, int limit, int resultSetHoldability) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic PreparedStatement prepareStatement (String SQL, int autoGeneratedKeys) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic PreparedStatement prepareStatement (String SQL, int [] columnIndexes) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic PreparedStatement prepareStatement (String SQL, String [] columnNames) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic Clob createClob () throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic Blob createBlob () throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic NClob createNClob () throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic SQLXML release () throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic boolean isValid (int timeout) throws SQLException {// TODO Auto-generated method stubreturn false ;} @ Overridepublic void setClientInfo (String name, String value) throws SQLClientInfoException {// TODO Auto-generated method stub} @ Overridepublic void setClientInfo (Properties properties Properties) throws SQLClientInfoException {// TODO Auto-generated method stub} @ Overridepublic String getClientInfo (String name) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic Properties getClientInfo () throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic Array createArrayOf (String typeName, Object [] elements) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic Struct createStruct (String typeName, Object [] attributes) throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic void setSchema (String schema) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic String getSchema () throws SQLException {// TODO Auto-generated method stubreturn null;} @ Overridepublic void abort (Executor executor) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic void setNetworkTimeout (Executor executor, int milliseconds) throws SQLException {// TODO Auto-generated method stub} @ Overridepublic int getNetworkTimeout () throws SQLException {// TODO Auto-generated method stubreturn 0 ;}}
          
         
        
       
      
     
    
   
  
 

Test code

Package tk. dong. connectionPool. test; import java. SQL. connection; import java. SQL. SQLException; import org. junit. test; import tk. dong. connection. util. jdbcPool; public class TestJdbcPool {@ Testpublic void jdbcPool () throws SQLException {// create a connection pool object JdbcPool jdbcPool = new JdbcPool (); // obtain the connection object jdbcPool from the connection pool. getConnection (); // obtain the connection object jdbcPool multiple times. getConnection (); jdbcPool. getConnection (); Connection conn = jdbcPool. getConnection (); // return the used connection object conn. close (); // obtain the connection object jdbcPool again. getConnection (); jdbcPool. getConnection (); jdbcPool. getConnection (); jdbcPool. getConnection ();}}

Test output result

The connection pool has already been added: 1 ::::::::: 2: :::::::::::: link object connection pool has been added: :::::::: 3 :::::::::: connection object connection pool has been added: 4 :::::::::::: the connection object connection pool has been added :::: :::::: 5 ::::::::::::: link object connection pool already added: ::::::: 6 ::::: ::::: the link object connection pool has been added: :::::::: 7 :::::::::: link object connection pool has been added: :::::::::: 8 ::::: ::::: 9 ::::::::::::: link object connection pool already added :::::: :::: a link object and a connection object are taken away: ::::: the connection pool has nine connection objects and another connection object is taken away ::::::: the connection pool also has eight connection objects and one connection object is taken away: the connection pool has seven connection objects and another connection object is taken away ::::::: there are also 6 connection objects in the connection pool. One connection object is used up and has been returned to the connection pool. Now, another connection object in the connection pool is = 7 and has been taken away ::::::: the connection pool also has 6 connection objects and one connection object is taken away: the connection pool has 5 connection objects and another connection object is taken away ::::::: there are four connection objects in the connection pool, and one connection object is taken away: :::: the connection pool has three connection objects.