我正在使用Java Web服务（Apache Axis）连接到Postgres数据库，并使用JDBC连接获取数据。但是在大多数情况下，我会突然收到一个org.postgresql.util.PSQLException：连接尝试失败的异常，有时它能正常工作。在这里，我使用了许多预处理语句。我的示例代码如下：
Connection connection=null;
try
{
Class.forName(driver);
connection = DriverManager.getConnection(url, username, password);
ps1=connection.prepareStatement("select * from emp");
rs1=ps1.executeQuery();
while(rs1.next())
{
ps2=connection.prepareStatement("select * from dept where dept_no="+rs1.getInt("dept_no"));
rs2=ps2.executeQuery();
while(rs2.next())
{
................
................
}
}
}
catch(Exception e)
{
System.out.println("Exception occurred is"+e.getMessage());
}
finally
{
try{if(rs1!=null)rs1.close();}catch(Exception e){ System.out.println("*1closing error--->"+e);}
try{if(ps1!=null)ps1.close();}catch(Exception e){ System.out.println("**1closing error--->"+e);}
try{if(rs2!=null)rs2.close();}catch(Exception e){ System.out.println("*2closing error--->"+e);}
try{if(ps2!=null)ps2.close();}catch(Exception e){ System.out.println("**2closing error--->"+e);}
try{if(connection!=null)connection.close();}catch(Exception e){ System.out.println("***closing error--->"+e);}
}
这个异常的堆栈跟踪如下：
org.postgresql.util.PSQLException: The connection attempt failed.
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:137)
at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:66)
at org.postgresql.jdbc2.AbstractJdbc2Connection.<init>(AbstractJdbc2Connection.java:124)
at org.postgresql.jdbc3.AbstractJdbc3Connection.<init>(AbstractJdbc3Connection.java:30)
at org.postgresql.jdbc3.Jdbc3Connection.<init>(Jdbc3Connection.java:24)
at org.postgresql.Driver.makeConnection(Driver.java:386)
at org.postgresql.Driver.connect(Driver.java:260)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at com.codon.service.WareHouseServer.get_picks(WareHouseServer.java:7415)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.axis.providers.java.RPCProvider.invokeMethod(RPCProvider.java:397)
at org.apache.axis.providers.java.RPCProvider.processMessage(RPCProvider.java:186)
at org.apache.axis.providers.java.JavaProvider.invoke(JavaProvider.java:323)
at org.apache.axis.strategies.InvocationStrategy.visit(InvocationStrategy.java:32)
at org.apache.axis.SimpleChain.doVisiting(SimpleChain.java:118)
at org.apache.axis.SimpleChain.invoke(SimpleChain.java:83)
at org.apache.axis.handlers.soap.SOAPService.invoke(SOAPService.java:454)
at org.apache.axis.server.AxisServer.invoke(AxisServer.java:281)
at org.apache.axis.transport.http.AxisServlet.doPost(AxisServlet.java:699)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at org.apache.axis.transport.http.AxisServletBase.service(AxisServletBase.java:327)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Unknown Source)
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(Unknown Source)
at org.postgresql.core.VisibleBufferedInputStream.readMore(VisibleBufferedInputStream.java:135)
at org.postgresql.core.VisibleBufferedInputStream.ensureBytes(VisibleBufferedInputStream.java:104)
at org.postgresql.core.VisibleBufferedInputStream.read(VisibleBufferedInputStream.java:73)
at org.postgresql.core.PGStream.ReceiveChar(PGStream.java:259)
at org.postgresql.core.v3.ConnectionFactoryImpl.doAuthentication(ConnectionFactoryImpl.java:254)
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:95)
... 37 more
我检查了postgres日志，并在不同情况下发现了以下语句：
1.WARNING: worker took too long to start; cancelled.
2.无法重新连接到共享内存 (key=...., addr=.....)：487。
3.无法从客户端接收数据：由于目标计算机积极拒绝，无法建立连接。
4.意外的EOF在客户端连接上。
请帮忙。谢谢！
ps2和rs2的关闭语句。我已经在应用程序中完成了这个操作。 - Sasi Vara Prasad