连接关闭MYSQL后不允许任何操作 [英] No operations allowed after connection closed MYSQL

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问题描述

基本上我有：

String query = "SELECT * FROM table WHERE UNIQUEID=? AND DIR IS NOT NULL AND NAME IS NOT NULL AND PAGETYPE IS NOT NULL";
DBConnect Database = new DBConnect();
Connection con = null;
PreparedStatement ps = null;
ResultSet rs=null;
try {
    con = Database.getcon();
    ps = con.prepareStatement(query);
    ps.setString(1, URI);
    rs=ps.executeQuery();
    if(rs.next()){
    }
} finally {
    if(ps != null)
        ps.close();
    if(rs != null)
        rs.close();
    if(con != null)
        con.close();
}
query = "SELECT COUNTCOMMENTS FROM videosinfos WHERE UNIQUEID=?";
try {
    con = Database.getcon();
    ps = con.prepareStatement(query); // Getting error here
    rs=ps.executeQuery();
    ps.setString(1, URI);
    rs=ps.executeQuery();
    if(rs.next()){
        comments = rs.getInt(1);
    }
} finally {
    if(ps != null)
        ps.close();
    if(rs != null)
        rs.close();
    if(con != null)
        con.close();
}

注意：我收到错误的行，对其进行评论。

Note: The line I get the error, have a comment on it.

连接到数据库：

public DBConnect(){
    try{
        Class.forName("com.mysql.jdbc.Driver");

        String unicode="useSSL=false&autoReconnect=true&useUnicode=yes&characterEncoding=UTF-8";
        con = DriverManager.getConnection("jdbc:mysql://localhost:15501/duckdb?"+unicode, "root", "_PWD");
        st = con.createStatement();
    }catch(Exception ex){
        System.out.println(ex.getMessage());
        System.out.println("couldn't connect!");
    }
}
public Connection getcon(){
    DBConnect condb = new DBConnect();
    Connection connect = con;
    return con;
}

但在汇编中我收到此错误：

But in compilation I get this error:


com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException：连接关闭后不允许任何操作。
在sun.reflect.GeneratedConstructorAccessor18.newInstance（来源不明）
在sun.reflect.DelegatingConstructorAccessorImpl.newInstance（DelegatingConstructorAccessorImpl.java:45）
在java.lang.reflect.Constructor.newInstance（ Constructor.java:423）
at com.mysql.jdbc.Util.handleNewInstance（Util.java:404）
at com.mysql.jdbc.Util.getInstance（Util.java:387)
at com.mysql.jdbc.SQLError.createSQLException（SQLError.java:917）
at com.mysql.jdbc.SQLError.createSQLException（SQLError.java:896）
at com.mysql.jdbc .SQLError.createSQLException（SQLError.java:885）
在com.mysql.jdbc.SQLError.createSQLException（SQLError.java:860）
在com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException（ConnectionImpl.java ：1246）
at com.mysql.jdbc.ConnectionImpl.checkClosed（ConnectionImpl.java:1241）
at com.mysql.jdbc.ConnectionImpl.prepareStatement（ConnectionImpl.java:4102)
at com.my sql.jdbc.ConnectionImpl.prepareStatement（ConnectionImpl.java:4071）
at duck.reg.pack.DBConnect.getitemfull_details（DBConnect.java:686）
at duck.reg.pack.index.doPost（ index.java:73）
at javax.servlet.http.HttpServlet.service（HttpServlet.java:661）
at javax.servlet.http.HttpServlet.service（HttpServlet.java:742)$ b在org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:231）
$ b在org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:166）
。在组织.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:52）
在org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:193）
在org.apache .catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:166）
处org.apache.catalina org.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:198）
。 core.StandardContextValve.invoke（StandardContextValve.java:96）
处org.apache.catalina.core.StandardHostValve org.apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase.java:478）
。在org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:80）
at org.apache.catalina.valves.AbstractAccessLogValve.invoke（AbstractAccessLogValve。）中调用（StandardHostValve.java:140)
。 java：624）
at org.apache.catalina.core.StandardEngineValve.invoke（StandardEngineValve.java:87）
at org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:342）
at org.apache.coyote.http11.Http11Processor.service(http11Processor.java:799)
at org.apache.coyote.AbstractProcessorLight.process（AbstractProcessorLight.java:66）
at org .apache.coyote.AbstractProtocol $ ConnectionHandler.process（AbstractProtocol.java:868）
at org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.doRun（Nio） Endpoint.java:1455）
at org.apache.tomcat.util.net.SocketProcessorBase.run（SocketProcessorBase.java:49）
at java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java: 1149）
在java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:624）
at org.apache.tomcat.util.threads.TaskThread $ WrappingRunnable.run（TaskThread.java： 61）
在java.lang.Thread.run（Thread.java:748）

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed. at sun.reflect.GeneratedConstructorAccessor18.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at com.mysql.jdbc.Util.handleNewInstance(Util.java:404) at com.mysql.jdbc.Util.getInstance(Util.java:387) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:917) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:896) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:885) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:860) at com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException(ConnectionImpl.java:1246) at com.mysql.jdbc.ConnectionImpl.checkClosed(ConnectionImpl.java:1241) at com.mysql.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:4102) at com.mysql.jdbc.ConnectionImpl.prepareStatement(ConnectionImpl.java:4071) at duck.reg.pack.DBConnect.getitemfull_details(DBConnect.java:686) at duck.reg.pack.index.doPost(index.java:73) at javax.servlet.http.HttpServlet.service(HttpServlet.java:661) at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:748)

我正在使用Debian MariaDB v10.x / Mysql

I'm Using Debian with MariaDB v10.x/Mysql

推荐答案

这是因为两个原因：


  • 执行第一个 PreparedStatement

  • getcon <后连接已关闭/ code>使用实例变量而不是 local 变量。因此，当下次调用 getcon 时，会返回相同的 conn 变量（之前关闭的变量）。

  • Connection is closed after the execution of first PreparedStatement
  • getcon uses an instance variable instead of local variable. Due to this, same conn variable (the one that was closed earlier) gets returned when getcon is called next time.

要解决此问题， getcon 和 DBConnect 需要修改以声明本地 conn 变量并返回它（事实上，你不需要 DBConnect ，例如：

To fix this, getcon and DBConnect need to be modified to declare a local conn variable and return it (in fact, you don't need DBConnect at all), e.g.:

public Connection getcon(){
    try{
        Class.forName("com.mysql.jdbc.Driver");
        String unicode="useSSL=false&autoReconnect=true&useUnicode=yes&characterEncoding=UTF-8";
        return DriverManager.getConnection("jdbc:mysql://localhost:15501/duckdb?"+unicode, "root", "_PWD");
    }catch(Exception ex){
        System.out.println(ex.getMessage());
        System.out.println("couldn't connect!");
        throw new RuntimeException(ex);
    }
}

这篇关于连接关闭MYSQL后不允许任何操作的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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