数据源拒绝建立连接，来自服务器的消息：“连接太多”
我正在尝试使用连接池库连接到我的数据库： DBPool 。 这是我的源代码。
DBUtils.java
package DB; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import javax.sql.ConnectionPoolDataSource; import snaq.db.ConnectionPool; import com.mysql.jdbc.Driver; /** * @author decorrea */ public class DBUtils { public static String jdbc_driver_name = "com.mysql.jdbc.Driver"; private static String server_name ; private static String database; private static String username; private static String password; public String getServer_name() { return server_name; } public void setServer_name(String serverName) { server_name = serverName; } public String getDatabase() { return database; } public void setDatabase(String database) { this.database = database; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } /* * Creates a MySQL DB connection from a pool */ public Connection createConnection(ConnectionPool pool){ Connection connection = null; try { // Load the JDBC driver Class driver_class = Class.forName(jdbc_driver_name); Driver driver = (Driver)driver_class.newInstance(); DriverManager.registerDriver(driver); connection = pool.getConnection(); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InstantiationException e) { e.printStackTrace(); } return connection; } /* * Creates a MySQL DB connection */ public Connection createConnection(){ Connection connection = null; try { // Load the JDBC driver Class driver_class = Class.forName(jdbc_driver_name); Driver driver = (Driver)driver_class.newInstance(); DriverManager.registerDriver(driver); String url = "jdbc:mysql://" + server_name + "/" + database; connection = DriverManager.getConnection(url); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InstantiationException e) { e.printStackTrace(); } return connection; } } TwitterAPI.java
/** * @author decorrea */ public class TwitterAPI { private static String server_name = "127.0.0.1"; private static String twitter_databse = "twitter"; private static String username = "root"; private static String password = "password"; public static Connection startDBConnection(String server_name, String database, String username, String password) { //Set DB parameters DBUtils mysql_obj = setDBParams(server_name, database, username, password); String url = "jdbc:mysql://" + server_name + "/" + database; ConnectionPool pool = new ConnectionPool("local",1, 1, 1, 180000, url, username, password); Connection connection = mysql_obj.createConnection(pool); return connection; } public static DBUtils setDBParams(String server_name, String database, String username, String password){ DBUtils mysql_obj = new DBUtils(); mysql_obj.setServer_name(server_name); mysql_obj.setDatabase(database); mysql_obj.setUsername(username); mysql_obj.setPassword(password); return mysql_obj; } public static String getTweets(BigInteger id){ Connection connection = startDBConnection(server_name,twitter_databse,username,password); ResultSet resultSet = null; String tweet = new String(); try { Statement statement = connection.createStatement(); String query = SQL_queries.get_tweets_on_id + id.toString(); //Execute the query resultSet = statement.executeQuery(query); while(resultSet.next()){ tweet = resultSet.getString("content"); } resultSet.close(); statement.close(); } catch (SQLException e) { e.printStackTrace(); } finally{ try { connection.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } return tweet; } }
我是连接池业务的新手，并且决定这样做只是因为我没有收到“通信链路故障”。
更新1：要添加我还尝试了Apache DBCP并尝试了此示例但仍然收到相同的错误。
org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Data source rejected establishment of connection, message from server: "Too many connections") at org.apache.commons.dbcp.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:1549) at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1388) at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044) at Twitter.TwitterAPI.startDBConnection(TwitterAPI.java:55) at Twitter.TwitterAPI.getTweets(TwitterAPI.java:84) at Twitter.TwitterAPI.main(TwitterAPI.java:235) Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data source rejected establishment of connection, message from server: "Too many connections" at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:45) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:528) at com.mysql.jdbc.Util.handleNewInstance(Util.java:409) at com.mysql.jdbc.Util.getInstance(Util.java:384) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1015) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:984) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1105) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2186) at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:787) at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:49) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:45) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:528) at com.mysql.jdbc.Util.handleNewInstance(Util.java:409) at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:357) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285) at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38) at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:582) at org.apache.commons.dbcp.BasicDataSource.validateConnectionFactory(BasicDataSource.java:1556) at org.apache.commons.dbcp.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:1545) ... 5 more Exception in thread "main" java.lang.NullPointerException at Twitter.TwitterAPI.getTweets(TwitterAPI.java:108) at Twitter.TwitterAPI.main(TwitterAPI.java:235)
我还检查了MySQL中my.ini文件中的max_connections变量。 这是它的价值：
MySQL服务器允许的最大并发会话数。 其中一个连接将保留给具有SUPER权限的用户，即使已达到连接限制，也允许管理员登录。
max_connections=100
MySQL终端上的show processlist命令显示处于hibernate状态的101个进程。
任何forms的帮助/评论将不胜感激
更新2 – 解决方案::所以，我找到了解决方案。 我没有在数据库的url连接中提到端口名称。
String url = "jdbc:mysql://" + server_name + "/" + database;
可能因此导致许多泄漏的联系。 完成后，我尝试了这里给出的例子。 它现在不会抛出任何错误。 感谢BalusC，我认为这只是因为他对更改MySQL端口号的评论。 要添加，更改MySQL端口号的方法不是通过更改my.ini文件，而是通过在开始 – >程序 – > MySQL服务器5.1 – > MySQL服务器实例配置向导下运行MySQL实例配置向导。 有趣的是，当没有指定端口号并且程序运行顺利时，代码没有抛出任何错误。 也许，JDBC默认连接到3306。 如果有人对此有任何特别的想法，请分享。
有关我的完整源代码， 请参阅下面的答案
org.apache.commons.dbcp.SQLNestedException：无法创建PoolableConnectionFactory（数据源拒绝建立连接，来自服务器的消息：“连接太多”）
这表明某些东西正在泄漏连接。 即某些东西一直在获取（打开）连接而不关闭它们和/或返回连接池。 重新启动数据库以便它可以硬关闭所有打开的连接应该暂时解决问题。 修复某些内容以便在使用后正确关闭连接应永久解决问题。
虽然发布的JDBC代码没有遵循最佳习惯用法，但它看起来并不像是连接泄漏的原因。 可能数据库已经运行了几个小时/几天，并且您在早期测试期间获得了太多连接而没有关闭它们以便数据库用完它们。
所以，我找到了解决方案。 我没有在数据库的url连接中提到端口名称。
String url = "jdbc:mysql://" + server_name + "/" + database;
可能因此导致许多泄漏的联系。 完成后，我尝试了这里给出的例子。 它现在不会抛出任何错误。 感谢BalusC，我认为这只是因为他对更改MySQL端口号的评论。 要添加，更改MySQL端口号的方法不是通过更改my.ini文件，而是通过在开始 – >程序 – > MySQL服务器5.1 – > MySQL服务器实例配置向导下运行MySQL实例配置向导。 有趣的是，当没有指定端口号并且程序运行顺利时，代码没有抛出任何错误。 也许，JDBC默认连接到3306。 如果有人对此有任何特别的想法，请分享。
为了人们的利益，这里是源代码：
DBUtils.java
package DB; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import javax.sql.DataSource; import org.apache.commons.dbcp.BasicDataSource; import com.mysql.jdbc.Driver; /** * @author decorrea * */ public class DBUtils { public static String jdbc_driver_name = "com.mysql.jdbc.Driver"; private static String server_name ; private static String database; private static String username; private static String password; private static int maxActive = 20; private static int maxIdle = 2 ; public String getServer_name() { return server_name; } public void setServer_name(String serverName) { server_name = serverName; } public String getDatabase() { return database; } public void setDatabase(String database) { this.database = database; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public static DataSource getDataSource(String server_name, String database, String username, String password){ BasicDataSource datasource = new BasicDataSource(); datasource.setDriverClassName(jdbc_driver_name); String url = "jdbc:mysql://" + server_name + "/" + database; System.out.println(url); datasource.setUsername(username); datasource.setPassword(password); datasource.setUrl(url); datasource.setMaxActive(maxActive); datasource.setMaxIdle(maxIdle); return datasource; } }
TwitterAPI.java
public class TwitterAPI { private static String server_name = "localhost:7777"; private static String twitter_databse = "twitter"; private static String username = "root"; private static String password = "password"; public static String twitter_unique_usernames_file = "twitter_unique_usernames_file.txt"; public static String language_model_file = "C:\\de\\JARS\\lingpipe-4.0.0\\demos\\models\\langid-leipzig.classifier"; public static DataSource dataSource = DBUtils.getDataSource(server_name, twitter_databse, username, password); public static Connection startDBConnection(String server_name, String database, String username, String password) { //Set DB parameters //DBUtils mysql_obj = setDBParams(server_name, database, username, password); Connection connection = null; //connection = mysql_obj.createConnection(); try { connection = dataSource.getConnection(); } catch (SQLException e) { e.printStackTrace(); } return connection; } public static DBUtils setDBParams(String server_name, String database, String username, String password){ DBUtils mysql_obj = new DBUtils(); mysql_obj.setServer_name(server_name); mysql_obj.setDatabase(database); mysql_obj.setUsername(username); mysql_obj.setPassword(password); return mysql_obj; } public static String getTweets(BigInteger id){ Connection connection = startDBConnection(server_name,twitter_databse,username,password); ResultSet resultSet = null; String tweet = new String(); try { Statement statement = connection.createStatement(); String query = SQL_queries.get_tweets_on_id + id.toString(); //Execute the query resultSet = statement.executeQuery(query); while(resultSet.next()){ tweet = resultSet.getString("content"); } resultSet.close(); statement.close(); } catch (SQLException e) { e.printStackTrace(); } finally{ try { connection.close(); } catch (SQLException e) { e.printStackTrace(); } } return tweet; }
希望这可以帮助。