Question

我正在尝试开发一个需要通过java servlet连接到远程数据库as400的android应用程序，并将JSON对象返回给用户。

这是我的DoGet方法代码：

protected void doGet(HttpServletRequest request,HttpServletResponse response) throws       ServletException, IOException {
    response.setContentType("application/json");
    PrintWriter out = response.getWriter();
    out.println("{");

    Connection conn = null;
    try {
    Class.forName("com.ibm.as400.access.AS400JDBCDriver").newInstance();
        conn = DriverManager.getConnection( "jdbc:as400://ipaddress;database name=dbname", "username", "password");
        System.out.println("Connected to the database");
    } catch (Exception e) {
        System.out.println("error! 1");
        e.printStackTrace();
    }


    try {
        conn.close();
        System.out.println("Disconnected from database");
    } catch (Exception e) {
        System.out.println("error! 2");
        e.printStackTrace();
    }

}

在我通过eclipse启动servlet之后，它停在“Class.forName（....）”并且它给了我以下错误：错误！ 1 java.sql.SQLException：应用程序请求者无法建立连接。（连接超时：连接）

at com.ibm.as400.access.JDError.throwSQLException(JDError.java:565)
at com.ibm.as400.access.AS400JDBCConnection.setProperties(AS400JDBCConnection.java:3332)
at com.ibm.as400.access.AS400JDBCDriver.prepareConnection(AS400JDBCDriver.java:1393)
at com.ibm.as400.access.AS400JDBCDriver.initializeConnection(AS400JDBCDriver.java:1230)
at com.ibm.as400.access.AS400JDBCDriver.connect(AS400JDBCDriver.java:371)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at it.liuc.webtest.Servlet1.doGet(Servlet1.java:31)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
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:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Unknown Source)
Caused by: java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
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 com.ibm.as400.access.PortMapper.getSocketConnection(PortMapper.java:273)
at com.ibm.as400.access.PortMapper.getServerSocket(PortMapper.java:161)
at com.ibm.as400.access.AS400ImplRemote.signonConnect(AS400ImplRemote.java:2334)
at com.ibm.as400.access.AS400ImplRemote.signon(AS400ImplRemote.java:2250)
at com.ibm.as400.access.AS400.sendSignonRequest(AS400.java:3042)
at com.ibm.as400.access.AS400.promptSignon(AS400.java:2606)
at com.ibm.as400.access.AS400.signon(AS400.java:3921)
at com.ibm.as400.access.AS400.connectService(AS400.java:1175)
at com.ibm.as400.access.AS400JDBCConnection.setProperties(AS400JDBCConnection.java:3324)
... 20 more
java.lang.NullPointerException
at it.liuc.webtest.Servlet1.doGet(Servlet1.java:43)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
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:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Unknown Source)

似乎它无法连接到服务器，但我确信用户名，密码和dbname是正确的。我必须在IP地址之后插入一个端口吗？还有其他建议吗？

感谢您的回答！

Answer 1

堆栈跟踪中的ConnectionTimedOut使其看起来像是

AS / 400未配置为回复TCP连接
中间某处有防火墙

从应用服务器计算机上，尝试telnet到数据库服务器中的AS / 400端口，看看它是否连接（即使它自动断开连接），或者它是否只是挂起。您可以使用Wireshark查看更详细的内容。

Answer 2

它停在“Class.forName（....）”

这是不正确的。那条线被执行了;如果失败，您会看到ClassNotFoundException。

您正在尝试执行连接所在的行。这就是失败的原因。

检查您正在使用的网址。我还要确保您运行的客户端计算机可以看到数据库服务器。你能从客户端机器ping数据库服务器吗？您可以使用某种非JDBC客户端连接到数据库吗？您是否有权使用您获得的凭据访问该数据库？拥有该数据库的DBA是否知道您的应用程序正在尝试连接它？

更新：为了确保我理解正确，你说你在运行Java客户端的机器上打开了命令shell并输入“ping ip-address”，其中“ip-address” “与您在连接URL中输入的值相同。

如果我在我的机器上打开命令shell并ping Google，它看起来像这样：

C:>ping www.google.com

Pinging www.l.google.com [74.125.130.147] with 32 bytes of data:

Reply from 74.125.130.147: bytes=32 time=29ms TTL=42
Reply from 74.125.130.147: bytes=32 time=27ms TTL=42
Reply from 74.125.130.147: bytes=32 time=29ms TTL=42
Reply from 74.125.130.147: bytes=32 time=28ms TTL=42

Ping statistics for 74.125.130.147:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 27ms, Maximum = 29ms, Average = 28ms

C:>

如果你没有，你有答案：你的客户端机器无法在网络上看到数据库服务器。

端口很重要，因为设置数据库的DBA可能没有使用默认端口。您需要与拥有数据库的人员交谈并对其进行排序。

Answer 3

您是否为此计划提供了正确的驱动程序库？首先，下载数据库连接驱动程序并导入程序。并创建与远程数据库的连接，并提供类路径和连接路径。然后在您的程序中，类路径和连接路径在您的程序中提供。运行你的程序。它会解决你的问题。

将servlet连接到数据库as400

3 个答案: