Question

我做错了什么？

我在win 7中运行Apache tomcat 7作为服务

我的jsp代码[... \ webapps \ test \ index.jsp]

<jsp:useBean id="Counter" scope="session" class="aaa.Counter" />
<html>
<title>sfcsv</title>

<%
    try{
        int x = Counter.read_count(),z = Counter.get_id();
        if(x%2==0)
            out.println(x + " = even");
        else
            out.println(x + " = odd");

        out.println(z);
    }catch(Exception e){
    out.println(e);
    }
%>


</html>

java代码[.. \ webapps \ test \ WEB-INF \ classes \ aaa \ Counter.java]

package aaa;

public class Counter {

    private int count;
    private static int instance_counter;
    private final int id;

    public Counter(){
        instance_counter ++;
        id = instance_counter;
        count = 0;
    }

    public int read_count(){
        return count++;
    }

    public int get_id(){
        return id;
    }

}

预期产出：

24 = even    1

我得到的输出：

24 = even

或

HTTP Status 500 - Unable to compile class for JSP: An error occurred at line: 8 in the jsp file: /index.jsp The method     get_id() is undefined for the type Counter 5: 6: <% 7: try{ 8: int x = Counter.read_count(),z = Counter.get_id(); 9:     if(x%2==0) 10: out.println(x + " = even"); 11: else Stacktrace:

type Exception report

message Unable to compile class for JSP: An error occurred at line: 8 in the jsp file: /index.jsp The method get_id()     is undefined for the type Counter 5: 6: <% 7: try{ 8: int x = Counter.read_count(),z = Counter.get_id(); 9: if(x%2==0)     10: out.println(x + " = even"); 11: else Stacktrace:

description The server encountered an internal error (Unable to compile class for JSP: An error occurred at line: 8 in     the jsp file: /index.jsp The method get_id() is undefined for the type Counter 5: 6: <% 7: try{ 8: int x =     Counter.read_count(),z = Counter.get_id(); 9: if(x%2==0) 10: out.println(x + " = even"); 11: else Stacktrace:) that     prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: Unable to compile class for JSP: 

An error occurred at line: 8 in the jsp file: /index.jsp
The method get_id() is undefined for the type Counter
5: 
6: <%
7:  try{
8:      int x = Counter.read_count(),z = Counter.get_id();
9:      if(x%2==0)
10:             out.println(x + " = even");
11:         else


Stacktrace:
    org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:102)
    org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:331)
    org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:469)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:378)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:353)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:340)
    org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:646)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:357)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.29 logs.

Apache Tomcat/7.0.29

编辑：重新启动计算机时问题消失

Answer 1

您已经解决了问题，但是这里有适当的选项可以让您重新加载或重新编译所有类和JSP文件，这可能有助于了解您的案例中发生了什么：

刷新Java类 - 确保在对类应用更改后重新编译类。另请参阅Web应用程序上下文的reloadable选项（默认为false）。

如果您希望Catalina监视/ WEB-INF / classes /和/ WEB-INF / lib中的类以进行更改，则设置为true;如果检测到更改，则自动重新加载Web应用程序。

刷新JSP文件 - 有关development变量的详细信息，请参阅Tomcat Jasper docs（默认为true，所以我猜这是你的价值所在）和modificationTestInterval变量（默认为4 seconds），您可以使用该变量设置检查JSP文件的更改间隔，并在必要时进行编译。两者通常都设置在$CATALINA_BASE/conf/web.xml。

Jasper是否在开发模式中使用？如果为true，则可以通过modificationTestInterval parameter.true或false指定检查JSP以进行修改的频率，默认为true。

Answer 2

我认为你的代码没问题。我认为你的IDE没有正确构建你的项目即.class文件未正确生成（或未生成）。所以尝试手动编译这个文件并将生成的.class文件放到项目的相应文件夹中，然后构建并重新启动你的服务器。检查是否构建它构建新的.JAR文件

最终变量在jsp中不起作用

2 个答案: