调试tomcat9.0.19源码

本文所用到的环境：

IntelliJ IDEA
Apache Maven 3.3.9
jdk1.8

1. 查看Tomcat版本

$TOMCAT_HOME\bin\version.bat

D:\Program_Files\apache-tomcat-9.0.19\bin>version.bat

Using CATALINA_BASE:   "D:\Program_Files\apache-tomcat-9.0.19"

Using CATALINA_HOME:   "D:\Program_Files\apache-tomcat-9.0.19"

Using CATALINA_TMPDIR: "D:\Program_Files\apache-tomcat-9.0.19\temp"

Using JRE_HOME:        "D:\Program Files\Java\jdk1.8.0_77"

Using CLASSPATH:       "D:\Program_Files\apache-tomcat-9.0.19\bin\bootstrap.jar;D:\Program_Files\apache-tomcat-9.0.19\bin\tomcat-juli.jar"

Server version: Apache Tomcat/9.0.19

Server built:   Apr 12 2019 14:22:48 UTC

Server number:  9.0.19.0

OS Name:        Windows 10

OS Version:     10.0

Architecture:   amd64

JVM Version:    1.8.0_77-b03

JVM Vendor:     Oracle Corporation

D:\Program_Files\apache-tomcat-9.0.19\bin>

这里使用的是JDK1.8，如果不是JDK1.8，则需要查看tomcat的兼容，选择适合自己的版本

2. 下载源码

根据自己的Tomcat版本，下载对应的源码

选择对应版本的tomcat，这里我使用的tomcat9，选择Archives

下载完成后解压，apache-tomcat-9.0.19-src

3. 创建项目结构

在D盘创建“D:\tomcat9.0.19”文件夹，然后将解压后的文件拷贝到该目录中，同时创建“catalina-home”目录
拷贝“apache-tomcat-9.0.19-src\conf”，到“catalina-home”目录下

创建“D:\tomcat9.0.19\pom.xml”文件

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>org.apache.tomcat</groupId>

    <artifactId>Tomcat9.0.19</artifactId>

    <name>Tomcat 9.0 Study</name>

    <version>1.0</version>

    <packaging>pom</packaging>

    <modules>

        <module>apache-tomcat-9.0.19-src</module>

    </modules>

</project>

创建“D:\tomcat9.0.19\apache-tomcat-9.0.19-src\pom.xml”文件

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0"

         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>org.apache.tomcat</groupId>

    <artifactId>Tomcat9.0</artifactId>

    <name>Tomcat9</name>

    <version>9.0</version>

    <build>

        <finalName>Tomcat9</finalName>

        <sourceDirectory>java</sourceDirectory>

        <resources>

            <resource>

                <directory>java</directory>

            </resource>

        </resources>

        <plugins>

            <plugin>

                <groupId>org.apache.maven.plugins</groupId>

                <artifactId>maven-compiler-plugin</artifactId>

                <version>2.3</version>

                <configuration>

                    <encoding>UTF-8</encoding>

                    <source>1.8</source>

                    <target>1.8</target>

                </configuration>

            </plugin>

        </plugins>

    </build>

    <dependencies>

        <dependency>

            <groupId>org.apache.ant</groupId>

            <artifactId>ant</artifactId>

            <version>1.9.5</version>

        </dependency>

        <dependency>

            <groupId>org.apache.ant</groupId>

            <artifactId>ant-apache-log4j</artifactId>

            <version>1.9.5</version>

        </dependency>

        <dependency>

            <groupId>org.apache.ant</groupId>

            <artifactId>ant-commons-logging</artifactId>

            <version>1.9.5</version>

        </dependency>

        <dependency>

            <groupId>javax.xml.rpc</groupId>

            <artifactId>javax.xml.rpc-api</artifactId>

            <version>1.1</version>

        </dependency>

        <dependency>

            <groupId>wsdl4j</groupId>

            <artifactId>wsdl4j</artifactId>

            <version>1.6.2</version>

        </dependency>

        <dependency>

            <groupId>org.eclipse.jdt.core.compiler</groupId>

            <artifactId>ecj</artifactId>

            <version>4.4</version>

        </dependency>

    </dependencies>

</project>

最终的目录结构为：

Administrator@git MINGW64 /d/tomcat9.0.19

$ ls -l                                                                                                                 total 6

drwxr-xr-x 1 Administrator 197121   0 3月  30 17:50 apache-tomcat-9.0.19-src

drwxr-xr-x 1 Administrator 197121   0 3月  30 17:41 catalina-home

-rw-r--r-- 1 Administrator 197121 533 3月  30 17:27 pom.xml

Administrator@git MINGW64 /d/tomcat9.0.19

$ ls -l catalina-home/                                                                                                  total 8

drwxr-xr-x 1 Administrator 197121 0 3月  30 17:38 conf

4. 将该项目导入到IDEA中

5. 编译

由于这里使用是JDK1.8，所以需要注释掉这些代码，否则容易报错：

编译：

6. 运行

1）创建Application

vm option 配置：

-Dfile.encoding=UTF-8 -Dcatalina.home=catalina-home -Dcatalina.base=catalina-home -Djava.endorsed.dirs=catalina-home/endorsed -Djava.io.tmpdir=catalina-home/temp -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.util.logging.config.file=catalina-home/conf/logging.properties

在Bootstrap的main方法当中加入测试代码：

 System.out.println("======================Tomcat Study======================");

下面是部分启动日志：

======================Tomcat Study======================

30-Mar-2020 17:38:32.009 警告 [main] org.apache.catalina.startup.ClassLoaderFactory.validateFile Problem with directory [D:\tomcat9.0.19\catalina-home\lib], exists: [false], isDirectory: [false], canRead: [false]

30-Mar-2020 17:38:32.017 警告 [main] org.apache.catalina.startup.ClassLoaderFactory.validateFile Problem with directory [D:\tomcat9.0.19\catalina-home\lib], exists: [false], isDirectory: [false], canRead: [false]

30-Mar-2020 17:38:32.017 警告 [main] org.apache.catalina.startup.ClassLoaderFactory.validateFile Problem with directory [D:\tomcat9.0.19\catalina-home\lib], exists: [false], isDirectory: [false], canRead: [false]

30-Mar-2020 17:38:32.017 警告 [main] org.apache.catalina.startup.ClassLoaderFactory.validateFile Problem with directory [D:\tomcat9.0.19\catalina-home\lib], exists: [false], isDirectory: [false], canRead: [false]

但是启动日志会有乱码，解决方法：

为何会有乱码：

原因：一般是中文编码不匹配导致；经跟踪，发现是ResourceBundle读取org\apache\catalina\startup\LocalStrings_zh_CN.properties文件时没有用utf8解码导致；

解决：修改org.apache.tomcat.util.res.StringManager类中的getString函数；

由
if (bundle != null) {

str = bundle.getString(key);

}
改为
if (bundle != null) {

str = new String(bundle.getString(key).getBytes(“ISO-8859-1”), “UTF-8”);

}
再次运行，一切正常

引用链接：http://www.itgather.com/archives/54

2）实验

在“catalina-home\webapps”目录中创建“demo\index.html”文件：

<html>

<head><title>Tomcat9.0.19_Test</title></head>

<body>

  <h1>Hello World!!!</h1> 

</body>

</html>

 访问： http://127.0.0.1:8080/demo/

在“catalina-home\webapps”目录中创建“demo\index.jsp”文件：

<%@ page contentType="text/html;charset=utf-8" pageEncoding="utf-8"%>

<html>

<head><title>Test-title</title></head>

<body>

<%

    request.setCharacterEncoding("utf-8");

    String method = request.getMethod() ;   // 取得提交方式

    String ip = request.getRemoteAddr() ;   // 取得客户端的IP地址

    String path = request.getServletPath() ;    // 取得访问路径

    String contextPath1= request.getContextPath() ; // 取得上下文资源名称

    String contextPath2 = getServletContext().getContextPath() ;// 取得上下文资源名称

    String realPath=getServletContext().getRealPath("/");//取得虚拟目录所对应的真实路径

%>

<h3>请求方式：<%=method%></h3>

<h3>IP地址：<%=ip%></h3>

<h3>访问路径：<%=path%></h3>

<h3>上下文名称1：<%=contextPath1%></h3>

<h3>上下文名称2：<%=contextPath2%></h3>

<h3>真实路径：<%=realPath%></h3>

</body>

</html>

访问： http://127.0.0.1:8080/demo/index.jsp

调试程序

index.jsp在被编译后会生成“index_jsp.java”和“index_jsp.class”文件，位置如下：

Administrator@git MINGW64 /d/tomcat9.0.19/catalina-home/work/Catalina/localhost/demo/org/apache/jsp

$ pwd

/d/tomcat9.0.19/catalina-home/work/Catalina/localhost/demo/org/apache/jsp

Administrator@git MINGW64 /d/tomcat9.0.19/catalina-home/work/Catalina/localhost/demo/org/apache/jsp

$ ls index_jsp.java

index_jsp.java

Administrator@git MINGW64 /d/tomcat9.0.19/catalina-home/work/Catalina/localhost/demo/org/apache/jsp

$ ls index_jsp.class

index_jsp.class

下面是“index_jsp.java”文件的内容：

/*

 * Generated by the Jasper component of Apache Tomcat

 * Version: Apache Tomcat/9.0.x-dev

 * Generated at: 2020-03-30 10:23:23 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.*;

public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase

    implements org.apache.jasper.runtime.JspSourceDependent,

                 org.apache.jasper.runtime.JspSourceImports {

  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 static final java.util.Set<java.lang.String> _jspx_imports_packages;

  private static final java.util.Set<java.lang.String> _jspx_imports_classes;

  static {

    _jspx_imports_packages = new java.util.HashSet<>();

    _jspx_imports_packages.add("javax.servlet");

    _jspx_imports_packages.add("javax.servlet.http");

    _jspx_imports_packages.add("javax.servlet.jsp");

    _jspx_imports_classes = null;

  }

  private volatile javax.el.ExpressionFactory _el_expressionfactory;

  private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager;

  public java.util.Map<java.lang.String,java.lang.Long> getDependants() {

    return _jspx_dependants;

  }

  public java.util.Set<java.lang.String> getPackageImports() {

    return _jspx_imports_packages;

  }

  public java.util.Set<java.lang.String> getClassImports() {

    return _jspx_imports_classes;

  }

  public javax.el.ExpressionFactory _jsp_getExpressionFactory() {

    if (_el_expressionfactory == null) {

      synchronized (this) {

        if (_el_expressionfactory == null) {

          _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();

        }

      }

    }

    return _el_expressionfactory;

  }

  public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() {

    if (_jsp_instancemanager == null) {

      synchronized (this) {

        if (_jsp_instancemanager == null) {

          _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());

        }

      }

    }

    return _jsp_instancemanager;

  }

  public void _jspInit() {

  }

  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 {

    if (!javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {

      final java.lang.String _jspx_method = request.getMethod();

      if ("OPTIONS".equals(_jspx_method)) {

        response.setHeader("Allow","GET, HEAD, POST, OPTIONS");

        return;

      }

      if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method)) {

        response.setHeader("Allow","GET, HEAD, POST, OPTIONS");

        response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSP åªåè¸ GETãPOST æ HEADãJasper è¿åè¸ OPTIONS");

        return;

      }

    }

    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\n");

      out.write("<html>\r\n");

      out.write("<head><title>Test-title</title></head>\r\n");

      out.write("<body>\r\n");

    request.setCharacterEncoding("utf-8");

    String method = request.getMethod() ;   // 取得提交方式

    String ip = request.getRemoteAddr() ;   // 取得客户端的IP地址

    String path = request.getServletPath() ;    // 取得访问路径

    String contextPath1= request.getContextPath() ; // 取得上下文资源名称

    String contextPath2 = getServletContext().getContextPath() ;// 取得上下文资源名称

    String realPath=getServletContext().getRealPath("/");//取得虚拟目录所对应的真实路径

      out.write("\r\n");

      out.write("<h3>请求方式：");

      out.print(method);

      out.write("</h3>\r\n");

      out.write("<h3>IP地址：");

      out.print(ip);

      out.write("</h3>\r\n");

      out.write("<h3>访问路径：");

      out.print(path);

      out.write("</h3>\r\n");

      out.write("<h3>上下文名称1：");

      out.print(contextPath1);

      out.write("</h3>\r\n");

      out.write("<h3>上下文名称2：");

      out.print(contextPath2);

      out.write("</h3>\r\n");

      out.write("<h3>真实路径：");

      out.print(realPath);

      out.write("</h3>\r\n");

      out.write("</body>\r\n");

      out.write("</html>");

    } catch (java.lang.Throwable t) {

      if (!(t instanceof javax.servlet.jsp.SkipPageException)){

        out = _jspx_out;

        if (out != null && out.getBufferSize() != 0)

          try {

            if (response.isCommitted()) {

              out.flush();

            } else {

              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);

    }

  }

}

这些是JSP的内置对象，另外还有request和response内置对象，在方法参数上

    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;

下面是它们的赋值操作：

      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;

能够看到它们都是通过pageContext的对应方法来进行赋值的。

实际上我们也可以在界面上将这些内置对象打印出来：

test.jsp

<%@ page contentType="text/html" pageEncoding="GBK"%>

<%@ page import="java.util.*"%>	<!-- 导入java.util包 -->

<html>

<head><title>PageScope</title></head>

    <body>

            <h4>request：<%=request%></h4>

            <h4>session：<%=session%></h4>

            <h4>application：<%=application%></h4>

            <h4>response：<%=response%></h4>

            <h4>out：<%=out%></h4>

            <h4>config：<%=config%></h4>

            <h4>page：<%=page%></h4>

            <h4>pageContext：<%=pageContext%></h4>

            <h4>getException：<%=pageContext.getException()%></h4>

            <h4>getPage：<%=(pageContext.getPage()==page)%></h4>

            <h4>getRequest：<%=(pageContext.getRequest()==request)%></h4>

            <h4>getResponse：<%=(pageContext.getResponse()==response)%></h4>

            <h4>getSession：<%=(pageContext.getSession()==session)%></h4>

            <h4>getServletConfig：<%=(pageContext.getServletConfig()==config) %></h4>

            <h4>getServletContext：<%=(pageContext.getServletContext()==application)%></h4>

    </body>

</html>

运行结果：

再回到调试的问题上来，想要调试“index_jsp.java”，需要创建“org/apache/jsp”文件夹，然后将该文件移动到该文件夹下，打上断点就可以开始调试了：

3）注意

默认情况下解析JSP会报错

现象：

Type Exception Report

Message java.lang.NullPointerException

Description The server encountered an unexpected condition that prevented it from fulfilling the request.

Exception

org.apache.jasper.JasperException: java.lang.NullPointerException

	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:638)

	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:514)

	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)

	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)

	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)

Root Cause

java.lang.NullPointerException

	org.apache.jsp.index_jsp._jspService(index_jsp.java:165)

	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)

	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)

	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476)

	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)

	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)

	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)

Note The full stack trace of the root cause is available in the server logs.

问题分析和解决方法

原因是我们直接启动org.apache.catalina.startup.Bootstrap的时候没有加载org.apache.jasper.servlet.JasperInitializer，从而无法编译JSP。解决办法是在tomcat的源码org.apache.catalina.startup.ContextConfig中手动将JSP解析器初始化：

————————————————

版权声明：本文为CSDN博主「yehong1225」的原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接及本声明。

原文链接：https://blog.csdn.net/yekong1225/article/details/81000446
再次测试正常

4）切换到Tomcat主目录，将VM options修改为如下配置即可

-Dcatalina.home=apache-tomcat-9.0.19-src -Dcatalina.base=apache-tomcat-9.0.19-src

-Djava.endorsed.dirs=apache-tomcat-9.0.19-src/endorsed -Djava.io.tmpdir=apache-tomcat-9.0.19-src/temp

-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager

-Djava.util.logging.config.file=apache-tomcat-9.0.19-src/conf/logging.properties

参考链接：

巴特西