Java数据库连接池

浏览数：39 / 时间：2015年06月12日

　　写了个 Java数据库连接池，具备基本的功能点：

　　1、对池中活动连接的重用。

　　2、池满时的适时等待。

　　3、对空闲连接的适时关闭。

　　抛砖引玉，不吝赐教。

源码文件 DBConnection.java

 1 package db;
 2 
 3 import java.sql.Connection;
 4 import java.util.concurrent.atomic.AtomicBoolean;
 5 
 6 /**
 7  * 封装的连接
 8  * @author Linkwork, [email protected]
 9  * @since 2014年11月01日
10  */
11 public class DBConnection {
12     
13     /**
14      * 原生的连接
15      */
16     private Connection connection = null;
17     
18     /**
19      * 是否空闲
20      */
21     private AtomicBoolean idle = null;
22     
23     /**
24      * 最近一次的空闲开始时间
25      */
26     private volatile long idleStart = 0L;
27     
28     /**
29      * 标识
30      */
31     private int index = -1;
32     
33     public DBConnection(int index, Connection connection, boolean idle) {
34         this.index = index;
35         this.connection = connection;
36         this.idle = new AtomicBoolean(idle);
37     }
38     
39     public void release() {
40         if (this.idle.compareAndSet(false, true)) {
41             this.idleStart = System.currentTimeMillis();
42         }
43     }
44 
45     public Connection getConnection() {
46         return connection;
47     }
48 
49     public AtomicBoolean getIdle() {
50         return idle;
51     }
52     
53     public void setConnection(Connection connection) {
54         this.connection = connection;
55     }
56 
57     public int getIndex() {
58         return index;
59     }
60 
61     public long getIdleStart() {
62         return idleStart;
63     }
64 
65     public void setIdleStart(long idleStart) {
66         this.idleStart = idleStart;
67     }
68     
69 }

源码文件 DBConnectionPool.java

  1 package db;
  2 
  3 import java.sql.Connection;
  4 import java.sql.DriverManager;
  5 import java.util.Vector;
  6 
  7 /**
  8  * 数据库连接池
  9  * @author Linkwork, [email protected]
 10  * @since 2014年11月01日
 11  */
 12 public class DBConnectionPool extends Thread {
 13     
 14     /**
 15      * 容量
 16      */
 17     private volatile int capacity = 1;
 18     
 19     /**
 20      * 驱动
 21      */
 22     private String driver = null;
 23     
 24     /**
 25      * 地址
 26      */
 27     private String url = null;
 28     
 29     /**
 30      * 用户名
 31      */
 32     private String user = null;
 33     
 34     /**
 35      * 密码
 36      */
 37     private String password = null;
 38     
 39     /**
 40      * 等待的轮询间隔
 41      */
 42     private volatile long waitInterval = 50L;
 43     
 44     /**
 45      * 等待的超时时间
 46      */
 47     private volatile long waitTimeout = 300000L;
 48     
 49     /**
 50      * 空闲的超时时间
 51      */
 52     private volatile long idleTimeout = 60L;
 53     
 54     /**
 55      * 连接集
 56      */
 57     private Vector<DBConnection> dbconnectionLst = null;
 58     
 59     /**
 60      * 是否关闭
 61      */
 62     private volatile boolean closing = false;
 63     
 64     public DBConnectionPool(
 65             int capacity,
 66             String driver,
 67             String url,
 68             String user,
 69             String password) {
 70         this.capacity = capacity;
 71         this.driver = driver;
 72         this.url = url;
 73         this.user = user;
 74         this.password = password;
 75         this.dbconnectionLst = new Vector<DBConnection>();
 76     }
 77     
 78     public DBConnection getDBConnection() throws Exception {
 79         long start = System.currentTimeMillis();
 80         while (! this.closing) {
 81             // 遍历连接集，获取空闲、可用的连接
 82             for (DBConnection dbconnection: this.dbconnectionLst) {
 83                 if (dbconnection.getIdle().compareAndSet(true, false)) {
 84                     // 若连接未关闭
 85                     if ((null != dbconnection.getConnection())
 86                             && (! dbconnection.getConnection().isClosed())) {
 87                         return dbconnection;
 88                     } else {
 89                         dbconnection.getIdle().set(true);
 90                     }
 91                 }
 92             }
 93             // 若连接的总数未超出容量
 94             if ((this.dbconnectionLst.size() < this.capacity)
 95                     && (! this.closing)) {
 96                 synchronized (this.dbconnectionLst) {
 97                     DBConnection dbconnection = this.createDBConnection(this.dbconnectionLst.size() + 1);
 98                     this.dbconnectionLst.add(dbconnection);
 99                     return dbconnection;
100                 }
101             } 
102             // 遍历连接集，重用空闲、不可用的连接
103             for (DBConnection dbconnection: this.dbconnectionLst) {
104                 if (dbconnection.getIdle().compareAndSet(true, false)) {
105                     // 若连接已关闭
106                     if ((null == dbconnection.getConnection())
107                             || dbconnection.getConnection().isClosed()) {
108                         Connection connection = this.createConnection();
109                         dbconnection.setConnection(connection);
110                         return dbconnection;
111                     } else {
112                         dbconnection.getIdle().set(true);
113                     }
114                 }
115             }
116             // 延迟轮询
117             Thread.sleep(this.waitInterval);
118             long end = System.currentTimeMillis();
119             if (end - start > this.waitTimeout) {
120                 throw new Exception("ERROR_WAIT_TIMEOUT");
121             }
122             start = end;
123         } // while (! this.closing) {
124         return null;
125     }
126     
127     public void close() throws Exception {
128         this.closing = true;
129         boolean closed = false;
130         while (! closed) {
131             closed = true;
132             Thread.sleep(this.waitInterval);
133             // 遍历连接集，关闭所有连接
134             for (DBConnection dbconnection: this.dbconnectionLst) {
135                 if (dbconnection.getIdle().compareAndSet(true, false)) {
136                     closed = false;
137                     if ((null != dbconnection.getConnection())
138                             && (! dbconnection.getConnection().isClosed())) {
139                         dbconnection.getConnection().close();
140                     }
141                 }
142             }
143         } // while (true) {
144     }
145 
146     @Override
147     public void run() {
148         while (! this.closing) {
149             try {
150                 Thread.sleep(this.waitInterval);
151                 // 遍历连接集，适时关闭空闲连接
152                 for (DBConnection dbconnection: this.dbconnectionLst) {
153                     if (dbconnection.getIdle().get()
154                             && (dbconnection.getIdleStart() > 0)
155                             && (System.currentTimeMillis() - dbconnection.getIdleStart() > this.idleTimeout)) {
156                         if (dbconnection.getIdle().compareAndSet(true, false)) {
157                             if ((dbconnection.getIdleStart() > 0)
158                                 && (System.currentTimeMillis() - dbconnection.getIdleStart() > this.idleTimeout)) {
159                                 dbconnection.setIdleStart(0L);
160                                 dbconnection.getConnection().close();
161                                 System.out.println("【dbconnection-" + dbconnection.getIndex() + "】idle timeout.");
162                             }
163                             dbconnection.getIdle().set(true);
164                         }
165                     }
166                 }
167             } catch (Exception e) {
168                 e.printStackTrace();
169             }
170         }
171     }
172     
173     public int getCapacity() {
174         return capacity;
175     }
176 
177     public void setCapacity(int capacity) {
178         this.capacity = capacity;
179     }
180 
181     public long getWaitTimeout() {
182         return waitTimeout;
183     }
184 
185     public void setWaitTimeout(long waitTimeout) {
186         this.waitTimeout = waitTimeout;
187     }
188 
189     public long getIdleTimeout() {
190         return idleTimeout;
191     }
192 
193     public void setIdleTimeout(long idleTimeout) {
194         this.idleTimeout = idleTimeout;
195     }
196 
197     private DBConnection createDBConnection(int index) throws Exception {
198         return new DBConnection(index, this.createConnection(), false);
199     }
200     
201     private Connection createConnection() throws Exception {
202         Class.forName(this.driver);
203         return DriverManager.getConnection(this.url, this.user, this.password);
204     }
205 
206 }

源码文件 DBConnectionPoolTest.java

 1 package db;
 2 
 3 import java.sql.PreparedStatement;
 4 import java.sql.ResultSet;
 5 
 6 /**
 7  * 测试：数据库连接池
 8  * @author Linkwork, [email protected]
 9  * @since 2014年11月01日
10  */
11 public class DBConnectionPoolTest {
12     
13     public static void main(String[] args) throws Exception {
14         DBConnectionPool pool = new DBConnectionPool(3, "com.mysql.jdbc.Driver", "jdbc:mysql://localhost:3306/db", "Linkwork", "276247076");
15         pool.start();
16         DBConnection dbconnection = pool.getDBConnection();
17         if (null != dbconnection) {
18             dbconnection.getConnection().prepareStatement("create table if not exists test_pool (tp_value int);").execute();
19             dbconnection.release();
20         }
21         mockConcurrent(pool);
22         Thread.sleep(2000);
23         mockConcurrent(pool);
24         Thread.sleep(50);
25         pool.close();
26     }
27     
28     public static void mockConcurrent(DBConnectionPool pool) {
29         for (int index = 0; index < 10; ++ index) {
30             final int value = index;
31             Thread thread = new Thread() {
32                 public void run() {
33                     DBConnection dbconnection = null;
34                     try {
35                         dbconnection = pool.getDBConnection();
36                     } catch (Exception e) {
37                         e.printStackTrace();
38                     }
39                     if (null != dbconnection) {
40                         try {
41                             if (Math.random() > 0.5) {
42                                 PreparedStatement statement = dbconnection.getConnection().prepareStatement("insert into test_pool(tp_value) values(?);");
43                                 statement.setInt(1, value);
44                                 statement.execute();
45                                 dbconnection.release();
46                                 System.out.println("【dbconnection-" + dbconnection.getIndex() + "】insert: " + value);
47                             }
48                             else {
49                                 PreparedStatement statement = dbconnection.getConnection().prepareStatement("select * from test_pool where tp_value = ?;");
50                                 statement.setInt(1, value);
51                                 ResultSet rs = statement.executeQuery();
52                                 if ((null != rs)
53                                         && rs.next()) {
54                                     System.out.println("【dbconnection-" + dbconnection.getIndex() + "】query: " + rs.getInt(1));
55                                 } else {
56                                     System.out.println("【dbconnection-" + dbconnection.getIndex() + "】query: ");
57                                 }
58                                 dbconnection.release();
59                             }
60                         } catch (Exception e) {
61                             e.printStackTrace();
62                         }
63                     }
64                 }
65             };
66             thread.start();
67         }
68     }
69 
70 }

运行 DBConnectionPoolTest.java，控制台输出：

【dbconnection-1】query: 0
【dbconnection-1】query: 8
【dbconnection-1】query: 4
【dbconnection-2】insert: 2
【dbconnection-3】insert: 6
【dbconnection-2】insert: 3
【dbconnection-1】insert: 1
【dbconnection-1】insert: 9
【dbconnection-3】insert: 5
【dbconnection-2】insert: 7
【dbconnection-1】idle timeout.
【dbconnection-2】idle timeout.
【dbconnection-3】idle timeout.
【dbconnection-3】query: 3
【dbconnection-1】query: 1
【dbconnection-2】query: 0
【dbconnection-1】idle timeout.
【dbconnection-2】idle timeout.
【dbconnection-3】idle timeout.