Java 连接关闭后不允许进行任何操作
基本上,我有:Java 连接关闭后不允许进行任何操作,java,mysql,jdbc,Java,Mysql,Jdbc,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 { co
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:我得到错误的那一行,请对它发表评论
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;
}
但在编译过程中,我遇到了以下错误:
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException:连接关闭后不允许进行任何操作。
位于sun.reflect.GeneratedConstructorAccessor18.newInstance(未知源)
在sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
位于java.lang.reflect.Constructor.newInstance(Constructor.java:423)
位于com.mysql.jdbc.Util.HandleneInstance(Util.java:404)
位于com.mysql.jdbc.Util.getInstance(Util.java:387)
位于com.mysql.jdbc.SQLError.createSQLException(SQLError.java:917)
位于com.mysql.jdbc.SQLError.createSQLException(SQLError.java:896)
位于com.mysql.jdbc.SQLError.createSQLException(SQLError.java:885)
位于com.mysql.jdbc.SQLError.createSQLException(SQLError.java:860)
位于com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException(ConnectionImpl.java:1246)
位于com.mysql.jdbc.ConnectionImpl.checkClosed(ConnectionImpl.java:1241)
在com.mysql.jdbc.ConnectionImpl.prepareStatement上(ConnectionImpl.java:4102)
在com.mysql.jdbc.ConnectionImpl.prepareStatement上(ConnectionImpl.java:4071)
在duck.reg.pack.DBConnect.getitemfull\u详细信息(DBConnect.java:686)
位于duck.reg.pack.index.doPost(index.java:73)
位于javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
位于javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
位于org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
位于org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
位于org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
位于org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
位于org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
位于org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
位于org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
位于org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
位于org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
位于org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
位于org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624)
位于org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
位于org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
位于org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799)
位于org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
位于org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
位于org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455)
位于org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
位于java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
位于java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
位于org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
运行(Thread.java:748)
我在MariaDB v10.x/Mysql中使用Debian,原因有两个:
- 执行第一个
PreparedStatement
使用getcon
变量而不是实例
变量。因此,下次调用local
时,将返回相同的getcon
变量(先前关闭的变量)conn
getcon
和DBConnect
以声明本地conn
变量并返回它(实际上,您根本不需要DBConnect
),例如:
一个很好的方法是像这样使用一个try-finally块
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()){
}
query = "SELECT COUNTCOMMENTS FROM videosinfos WHERE UNIQUEID=?";
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();
}
这是一个MySQL设置问题。MySQL服务器的响应时间(上例中为60621毫秒)超过了MySQL服务器配置的等待超时值 解决方案 要解决此问题,请与MySQL数据库管理员一起增加wait_timeout参数的值 将Hibernate配置与MySQL服务器对齐以解决此问题
此设置可在my.cnf文件中配置。默认情况下,mysql将该值设置为“28800”秒。如果该值已从默认值被修改,考虑将其恢复到默认状态,以恢复到DATAMER服务器的连接。 JDBC标准在第一次代码> PrimeRealdS> < /C>之后不关闭连接。这只应在close()或错误条件下发生:
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()){
}
query = "SELECT COUNTCOMMENTS FROM videosinfos WHERE UNIQUEID=?";
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();
}