java--數據庫連接池3(多例)

用裝飾模式實現
批量創建與數據庫的連接，並把創建的連接加入List< Connection> pool對象中。
讓getConnection方法每次調用時，從pool中取一個Connection返回給用戶。
當用戶使用完Connection，調用Connection.close()方法時，Collection對象應保證將自己返回到pool中,而不要把conn還給數據庫。
所以Collection保證將自己返回到pool中是此處編程的難點。

package cn.hncu.pool;

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.SQLWarning;
import java.sql.SQLXML;
import java.sql.Savepoint;
import java.sql.Statement;
import java.sql.Struct;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.Executor;

public class ConnUtils2 {

    private final static List<Connection> pool=new ArrayList<Connection>();
    private final static int num=3;
    private ConnUtils2(){

    }
    static{
        Properties p=new Properties();
        try {
//          p.load(ConnUtils.class.getClassLoader().getResourceAsStream("jdbc.properties"));
            p.load(ClassLoader.getSystemResourceAsStream("jdbc.properties"));
            String driver=p.getProperty("driver");
            String url=p.getProperty("url");
            String name=p.getProperty("username");
            String pwd=p.getProperty("password");
            Class.forName(driver);
            for(int i=0;i<num;i++){
                Connection con=DriverManager.getConnection(url, name, pwd);
                //更改conn.close()方法
                myConnection conn = new myConnection(con);
                pool.add(conn);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //採用包裝模式(裝飾模式) 對Connection conn的功能進行增強
    //因爲要訪問ConnUtils2類中的靜態變量pool，因此要聲明成靜態內部類
    public static synchronized Connection getConnection(){
        if(pool.size()<=0){
            System.out.println("池中連接沒有了...");
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return getConnection();
        }
        return pool.remove(0);//拿一個移一個
    }

    public static class myConnection implements Connection{
        private Connection con;
        public myConnection(Connection con) {
            this.con=con;
        }

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

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

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

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

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

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

        @Override
        public void setAutoCommit(boolean autoCommit) throws SQLException {
            con.setAutoCommit(autoCommit);
        }

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

        @Override
        public void commit() throws SQLException {
            con.commit();
        }

        @Override
        public void rollback() throws SQLException {
            con.rollback();
        }

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

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

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

        @Override
        public void setReadOnly(boolean readOnly) throws SQLException {
            con.setReadOnly(readOnly);
        }

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

        @Override
        public void setCatalog(String catalog) throws SQLException {
            con.setCatalog(catalog);
        }

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

        @Override
        public void setTransactionIsolation(int level) throws SQLException {
            con.setTransactionIsolation(level);
        }

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

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

        @Override
        public void clearWarnings() throws SQLException {
            con.clearWarnings();
        }

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

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

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

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

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

        @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 {
            con.setNetworkTimeout(executor, milliseconds);
        }

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

    }
}

jdbc.properties

##MySQL
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/hncu?useUnicode=true&characterEncoding=utf-8
username=root
password=1234
size=3
##Oracle
#driver=oracle.jdbc.driver.OracleDriver
#url=jdbc:oracle:thin:@127.0.0.1:1521:orcl
#username=scott
#password=tiger

演示

package cn.hncu.tx;

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;

import cn.hncu.pool.ConnUtils2;
//使用的是多例的連接池ConnUtils
public class TxDemo3 {

    public static void main(String[] args) throws Exception {
        Connection con=ConnUtils2.getConnection();
        System.out.println("main線程獲得一個連接:"+con);
        Statement st = con.createStatement();

        try {
            con.setAutoCommit(false);
            st.execute("INSERT INTO person VALUES('P200','趙子龍','1')");

            new MyThread3(1).start();
            new MyThread3(2).start();
            new MyThread3(3).start();
            new MyThread3(4).start();
            new MyThread3(5).start();

            Thread.sleep(1000);

            con.commit();
            System.out.println("main線程提交一個事務....");
        } catch (Exception e) {
            con.rollback();
            System.out.println("main線程回滾一個事務.....");
        }finally{
            con.setAutoCommit(true);
            con.close();
        }

    }

}
class MyThread3 extends Thread{
    private int num;
    public MyThread3(int num){
        this.num = num;
    }
    @Override
    public void run() {
        Connection con=ConnUtils2.getConnection();
        System.out.println(num+"線程獲得一個連接:"+con);
        try {
            Statement st = con.createStatement();
            con.setAutoCommit(false);
            String sql = "INSERT INTO person VALUES('P09"+num+"','趙子龍','1')";
            if(num==3){
                sql = "INSERT INTO person VALUES('P09"+num+"'趙子龍','1')";
            }else{
                Thread.sleep(100);
            }
            st.executeUpdate(sql);
            con.commit();
            System.out.println(num+"線程提交一個事務....");
        } catch (Exception e) {
            try {
                con.rollback();
                System.out.println(num+"線程回滾一個事務.....");
            } catch (SQLException e1) {
                e1.printStackTrace();
            }
        }finally{
            try {
                con.setAutoCommit(true);
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
    }


    }

}