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Code  ›  tomcat编译超过64k大小的jsp文件报错原因开发者社区
apache servlet jsp
https://cloud.tencent.com/developer/article/1384409
谦和的机器人
1 年前
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SmileNicky
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tomcat编译超过64k大小的jsp文件报错原因

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社区首页 > 专栏 > Nicky's blog > tomcat编译超过64k大小的jsp文件报错原因

tomcat编译超过64k大小的jsp文件报错原因

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SmileNicky
发布 于 2019-01-17 16:22:30
916 0
发布 于 2019-01-17 16:22:30
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今天遇到一个问题,首先是在tomcat 中间件 上跑的web项目,一个jsp文件,因为代码行数实在是太多了,更新了几个版本之后编译报错了,页面打开都是报500的错误,500的报错,知道http协议返回码的都知道,这是服务端的报错。

jsp编译过程是先编译为servlet,然后再通过类加载器编译为.class文件,再执行为Servlet实例。这就是jsp的编译过程。所以jsp报500错误也可以理解,属于服务端的报错没什么好怀疑的。

服务端报错,肯定就是去console拿日志了。从CONSOLE拿到日志关键信息:

The code of method _jspService(HttpServletRequest, HttpServletResponse) is exceeding the 65535 bytes limit

这个报错意思大概是超过字节限制。通过网上资料搜索,很多地方都是给出了一个解决方法,不过大部分都没说明为什么。 网上一大堆差不多的博客,都是这样说的,在tomcat的conf文件夹里,找到web.xml,然后在JspServlet的servlet配置里,加上mappedfile参数 修改后的代码

<servlet>
        <servlet-name>jsp</servlet-name>
        <servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class>
        <init-param>
            <param-name>fork</param-name>
            <param-value>false</param-value>
        </init-param>
        <init-param>
            <param-name>xpoweredBy</param-name>
            <param-value>false</param-value>
        </init-param>
        <init-param>  
            <param-name>mappedfile</param-name>  
            <param-value>false</param-value>  
        </init-param> 
        <load-on-startup>3</load-on-startup>
    </servlet>

其实也就是加上

<init-param>  
           <param-name>mappedfile</param-name>  
           <param-value>false</param-value>  
 </init-param>

大部分博客并没有给出原因。不过还是可以解决问题的。不过网上所说的这种方法并不是很好的方法,只能说是暂缓之策。

首先要从jsp的编译说起,jsp经过tomcat编译后,文件会保存在哪里? 下面介绍一下,一般路径都会在${TOMCAT_HOME}\work\Catalina\localhost\项目名称\org\apache\jsp文件夹下面。 假如新建了一个index.jsp,经过编译之后,都会在该路径下面生成index_jsp.java文件和index_jsp.class文件,index_jsp.java文件是什么?其实可以理解为tomcat编译生成的servlet类,index_jsp.class呢?当然就是servlet类编译之后生成的.class文件了。 随便找个index_jsp.java文件,拿代码来看看:

/*
 * Generated by the Jasper component of Apache Tomcat
 * Version: Apache Tomcat/7.0.32
 * Generated at: 2016-11-19 03:26:12 UTC
 * Note: The last modified time of this file was set to
 *       the last modified time of the source file after
 *       generation to assist with modification tracking.
package org.apache.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.util.*;
public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase
    implements org.apache.jasper.runtime.JspSourceDependent {
  private static final javax.servlet.jsp.JspFactory _jspxFactory =
          javax.servlet.jsp.JspFactory.getDefaultFactory();
  private static java.util.Map<java.lang.String,java.lang.Long> _jspx_dependants;
  private javax.el.ExpressionFactory _el_expressionfactory;
  private org.apache.tomcat.InstanceManager _jsp_instancemanager;
  public java.util.Map<java.lang.String,java.lang.Long> getDependants() {
    return _jspx_dependants;
  public void _jspInit() {
    _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
    _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
  public void _jspDestroy() {
  public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
        throws java.io.IOException, javax.servlet.ServletException {
    final javax.servlet.jsp.PageContext pageContext;
    javax.servlet.http.HttpSession session = null;
    final javax.servlet.ServletContext application;
    final javax.servlet.ServletConfig config;
    javax.servlet.jsp.JspWriter out = null;
    final java.lang.Object page = this;
    javax.servlet.jsp.JspWriter _jspx_out = null;
    javax.servlet.jsp.PageContext _jspx_page_context = null;
    try {
      response.setContentType("text/html;charset=UTF-8");
      pageContext = _jspxFactory.getPageContext(this, request, response,
      			null, true, 8192, true);
      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();
      config = pageContext.getServletConfig();
      session = pageContext.getSession();
      out = pageContext.getOut();
      _jspx_out = out;
      out.write('\r');
      out.write('\n');
      if (true) {
        _jspx_page_context.forward("/login_toLogin");
        return;
      out.write('\r');
      out.write('\n');
    } catch (java.lang.Throwable t) {
      if (!(t instanceof javax.servlet.jsp.SkipPageException)){
        out = _jspx_out;
        if (out != null && out.getBufferSize() != 0)
          try { out.clearBuffer(); } catch (java.io.IOException e) {}
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
        else throw new ServletException(t);
    } finally {
      _jspxFactory.releasePageContext(_jspx_page_context);
}

从代码可以看出,类继承于HttpJspBase类实现JspSourceDependent接口,先看一下HttpJspBase类,这个类从哪来的呢?HttpJspBase是tomcat库提供的,所以拿tomcat库的源码来看看,在${TOMCAT_HOME}/lib里找到价包jasper.jar,反编译代码,找到HttpJspBase类

package org.apache.jasper.runtime;
import java.io.IOException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.HttpJspPage;
import org.apache.jasper.compiler.Localizer;
public abstract class HttpJspBase extends HttpServlet
  implements HttpJspPage
  private static final long serialVersionUID = 1L;
  public final void init(ServletConfig config)
    throws ServletException
    super.init(config);
    jspInit();
    _jspInit();
  public String getServletInfo()
    return Localizer.getMessage("jsp.engine.info");
  public final void destroy()
    jspDestroy();
    _jspDestroy();
  public final void service(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException
    _jspService(request, response);
  public void jspInit()
  public void _jspInit()
  public void jspDestroy()
  protected void _jspDestroy()
  public abstract void _jspService(HttpServletRequest paramHttpServletRequest, HttpServletResponse paramHttpServletResponse)
    throws ServletException, IOException;
}

代码并不是说多复杂,HttpJspBase类继承HttpServlet类,实现HttpJspPage接口,也就是说HttpJspBase重写了HttpServlet的service(),init()等等方法,HttpServlet,我们就很熟悉了。HttpJspPage又是什么?看它的包名,马上知道它是jdk提供的接口,马上找到它的代码:

/*
 * The contents of this file are subject to the terms
 * of the Common Development and Distribution License
 * (the "License").  You may not use this file except
 * in compliance with the License.
 * You can obtain a copy of the license at
 * glassfish/bootstrap/legal/CDDLv1.0.txt or
 * https://glassfish.dev.java.net/public/CDDLv1.0.html.
 * See the License for the specific language governing
 * permissions and limitations under the License.
 * When distributing Covered Code, include this CDDL
 * HEADER in each file and include the License file at
 * glassfish/bootstrap/legal/CDDLv1.0.txt.  If applicable,
 * add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your
 * [name of copyright owner]
package javax.servlet.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;
 * The HttpJspPage interface describes the interaction that a JSP Page
 * Implementation Class must satisfy when using the HTTP protocol.
 * The behaviour is identical to that of the JspPage, except for the signature
 * of the _jspService method, which is now expressible in the Java type
 * system and included explicitly in the interface.
 * @see JspPage
public interface HttpJspPage extends JspPage {
    /** The _jspService()method corresponds to the body of the JSP page. This
     * method is defined automatically by the JSP container and should never
     * be defined by the JSP page author.
     * If a superclass is specified using the extends attribute, that
     * superclass may choose to perform some actions in its service() method
     * before or after calling the _jspService() method.  See using the extends
     * attribute in the JSP_Engine chapter of the JSP specification.
     * @param request Provides client request information to the JSP.
     * @param response Assists the JSP in sending a response to the client.
     * @throws ServletException Thrown if an error occurred during the 
     *     processing of the JSP and that the container should take 
     *     appropriate action to clean up the request.
     * @throws IOException Thrown if an error occurred while writing the
     *     response for this page.
    public void _jspService(HttpServletRequest request,
 
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