那些遇到过的问题

数据源拒绝建立连接,来自服务器的消息:"连接太多"

Dex*_*ter 9 java mysql jdbc

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;
    }
}
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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;
    }
}
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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.<init>(ConnectionImpl.java:787)
    at com.mysql.jdbc.JDBC4Connection.<init>(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)
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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

的SHOW PROCESSLIST MySQL的终端上的命令显示在睡眠101个处理.

任何形式的帮助/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;
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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改变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,而是通过运行MySQL实例配置向导下开始- >程序- > MySQL服务器5.1 - > MySQL服务器实例配置向导.值得注意的是,当未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

Bal*_*usC 5

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，一些被泄露的连接。也就是说，某些东西会不断获取（打开）连接，而无需关闭它们和/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，应该暂时解决此问题。修复某些问题，以便在使用后正确关闭连接，应可以永久解决此问题。

尽管发布的JDBC代码没有遵循最佳习惯用法，但它看起来并不是造成连接泄漏的原因。数据库可能已经运行了数小时/天，并且您在较早的测试中获得了太多的连接而没有关闭它们，因此数据库用尽了它们。

Dex*_*ter 5

所以，我想出了解决办法。我没有在数据库连接的 url 中提到端口名称。

String url = "jdbc:mysql://" + server_name +  "/" + database;
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可能因此导致了许多连接泄漏。完成后，我尝试使用此处给出的示例。现在它不会抛出任何错误。感谢 BalusC，我只是因为他对更改 MySQL 端口号的评论而发现了这一点。补充一下，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 Server 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，当未指定端口号时，代码不会抛出任何错误，并且程序运行顺利。JDBC 可能默认连接到 3306。如果有人对此有任何特别的想法，请分享。

为了大家的利益，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;
    }
}
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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;
    }
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希望这可以帮助。

  • 对于仍然想知道此端口设置在哪里的人，请检查“TwitterAPI”中的“server_name”字段 (2认同)

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