Tomcat源码分析--源码搭建

喜欢ヅ旅行 2022-12-15 12:58 217阅读 0赞

# 1.前言 #

当时看Tomcat源码的初衷是想弄明白它里面的类加载器的那些事，感觉对于动态部署应用，他就废弃旧的类加载器，新建一个新的加载器去加载应用，感觉是一件很神奇的事，处于此好奇心，决定要看看他的实现思路。然而Tomcat源码环境很早就搭建了，后来由于工作忙一直还没来的及看。看了一周的源码，觉得不记录的东西总少些什么，正如有人说过，没有输出的学习永远都是浅显的。好吧，那就记录一下吧。

# 2.环境准备 #

## 2.1 开发工具准备 ##

1) Idea2018.2

2) jdk1.8.241

## 2.2 源码准备 ##

### 2.2.1 github地址 ###

https://github.com/apache/tomcat

### 2.2.2 选择版本 ###

我们主要是针对tomcat8进行分析，所以这里选择tomcat8的的8.5.59版本。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29ZaW5IZVpoaUd1YW5n_size_16_color_FFFFFF_t_70][]

### 2.2.3 下载源码 ###

1）复制源码地址，当然也可以下载zip包。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29ZaW5IZVpoaUd1YW5n_size_16_color_FFFFFF_t_70 1][]

2）通过git下载源码。由于我要对源码做注释，所以我直接下载的zip包，然后又上传到我自己的gitee上。这里大家可以自行选择，那我按照git clone的方式讲解吧。创建一个文件夹，执行如下命令：

git clone git@github.com:apache/tomcat.git

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29ZaW5IZVpoaUd1YW5n_size_16_color_FFFFFF_t_70 2][]

3)源码的目录结构

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29ZaW5IZVpoaUd1YW5n_size_16_color_FFFFFF_t_70 3][]

# 3. 源码构建 #

## 3.1 创建pom.xml文件 ##

通过上图的目录结构我们知道tomcat源码是通过ant构建的。这里我们便于构建，减少错误频次，决定在外边套一层maven。创建pom.xml文件，放到根目录下。

<?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</groupId>
        <artifactId>tomcat</artifactId>
        <name>apache-tomcat-8.5.58</name>
        <version>8.5.58</version>
    
        <build>
            <finalName>Tomcat-8.5.58</finalName>
            <sourceDirectory>java</sourceDirectory>
            <testSourceDirectory>test</testSourceDirectory>
            <resources>
                <resource>
                    <directory>java</directory>
                </resource>
            </resources>
            <testResources>
                <testResource>
                    <directory>test</directory>
                </testResource>
            </testResources>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.5.1</version>
                    <configuration>
                        <encoding>UTF-8</encoding>
                        <source>1.8</source>
                        <target>1.8</target>
                    </configuration>
                </plugin>
            </plugins>
        </build>
    
        <dependencies>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
                <scope>test</scope>
            </dependency>
            <dependency>
                <groupId>org.easymock</groupId>
                <artifactId>easymock</artifactId>
                <version>4.2</version>
                <scope>test</scope>
            </dependency>
    
            <dependency>
                <groupId>org.apache.ant</groupId>
                <artifactId>ant</artifactId>
                <version>1.10.0</version>
            </dependency>
            <dependency>
                <groupId>wsdl4j</groupId>
                <artifactId>wsdl4j</artifactId>
                <version>1.6.2</version>
            </dependency>
            <dependency>
                <groupId>javax.xml</groupId>
                <artifactId>jaxrpc</artifactId>
                <version>1.1</version>
            </dependency>
            <dependency>
                <groupId>org.eclipse.jdt.core.compiler</groupId>
                <artifactId>ecj</artifactId>
                <version>4.6.1</version>
            </dependency>
            
            <dependency>
                <groupId>org.glassfish</groupId>
                <artifactId>javax.xml.rpc</artifactId>
                <version>3.0.1-b03</version>
            </dependency>
    
        </dependencies>
    </project>

## 3.2 用过idea导入 ##

1)依次选择file->new->Project from Existing Sources...

![2020101709193461.png][]

2)选择刚才下载的源码。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29ZaW5IZVpoaUd1YW5n_size_16_color_FFFFFF_t_70 4][]

3）在弹出的对话框选择maven

![20201017092148673.png][]

4) 一直下一步，等待项目构建

## 3.3 项目运行测试 ##

### 3.3.1 配置启动类 ###

org.apache.catalina.startup.Bootstrap

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### 3.3.2 启动项目 ###

在启动项目的时候并没有那么顺利，还是还有一些错误。

1）启动项目报错，找不到CookieFilter

此时有两种解决方法，一种值直接删除TestCookieFilter类，在./test/util/TestCookieFilter。这是测试类，我们读源码一般很少用到这个类。当然考虑到源码的完整性，我们还是要把这个文件找到，在./test/util/下创建类CookieFilter。

/*
     * Licensed to the Apache Software Foundation (ASF) under one or more
     * contributor license agreements.  See the NOTICE file distributed with
     * this work for additional information regarding copyright ownership.
     * The ASF licenses this file to You under the Apache License, Version 2.0
     * (the "License"); you may not use this file except in compliance with
     * the License.  You may obtain a copy of the License at
     *
     *     http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */
    package util;
    
    import java.util.Locale;
    import java.util.StringTokenizer;
    
    /**
     * Processes a cookie header and attempts to obfuscate any cookie values that
     * represent session IDs from other web applications. Since session cookie names
     * are configurable, as are session ID lengths, this filter is not expected to
     * be 100% effective.
     *
     * It is required that the examples web application is removed in security
     * conscious environments as documented in the Security How-To. This filter is
     * intended to reduce the impact of failing to follow that advice. A failure by
     * this filter to obfuscate a session ID or similar value is not a security
     * vulnerability. In such instances the vulnerability is the failure to remove
     * the examples web application.
     */
    public class CookieFilter {
    
        private static final String OBFUSCATED = "[obfuscated]";
    
        private CookieFilter() {
            // Hide default constructor
        }
    
        public static String filter(String cookieHeader, String sessionId) {
    
            StringBuilder sb = new StringBuilder(cookieHeader.length());
    
            // Cookie name value pairs are ';' separated.
            // Session IDs don't use ; in the value so don't worry about quoted
            // values that contain ;
            StringTokenizer st = new StringTokenizer(cookieHeader, ";");
    
            boolean first = true;
            while (st.hasMoreTokens()) {
                if (first) {
                    first = false;
                } else {
                    sb.append(';');
                }
                sb.append(filterNameValuePair(st.nextToken(), sessionId));
            }
    
    
            return sb.toString();
        }
    
        private static String filterNameValuePair(String input, String sessionId) {
            int i = input.indexOf('=');
            if (i == -1) {
                return input;
            }
            String name = input.substring(0, i);
            String value = input.substring(i + 1, input.length());
    
            return name + "=" + filter(name, value, sessionId);
        }
    
        public static String filter(String cookieName, String cookieValue, String sessionId) {
            if (cookieName.toLowerCase(Locale.ENGLISH).contains("jsessionid") &&
                    (sessionId == null || !cookieValue.contains(sessionId))) {
                cookieValue = OBFUSCATED;
            }
    
            return cookieValue;
        }
    }

2）解决控制台输出乱码

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29ZaW5IZVpoaUd1YW5n_size_16_color_FFFFFF_t_70 6][]

修改代码：

org.apache.tomcat.util.res.StringManager#getString(final String key, final Object... args)

public String getString(final String key, final Object... args) {
    	String value = getString(key);
    	if (value == null) {
    		value = key;
    	}
        //-------------增加代码 start --------------------------------
    	try {
    		value = new String(value.getBytes("ISO-8859-1"),"UTF-8");
    	}catch (Exception e){
    		e.printStackTrace();
    	}
        //-------------增加代码 end --------------------------------
    	MessageFormat mf = new MessageFormat(value);
    	mf.setLocale(locale);
    	return mf.format(args, new StringBuffer(), null).toString();
    }

org.apache.jasper.compiler.Localizer#getMessage(java.lang.String)

public static String getMessage(String errCode) {
    	String errMsg = errCode;
    	try {
    		if (bundle != null) {
    			errMsg = bundle.getString(errCode);
    		}
    	} catch (MissingResourceException e) {
    	}
    	//------------------------增加代码 start ---------------------
    	try{
    		errMsg = new String(errMsg.getBytes("ISO-8859-1"),"UTF-8");
    	}catch (Exception e){
    	   e.printStackTrace();
    	}
    	//------------------------增加代码 end ---------------------
    	return errMsg;
    }

另外一种解决问题的思路,在vm中加入参数：

-Duser.language=en -Duser.region=US -Dfile.encoding=UTF-8

3）java.lang.ClassNotFoundException: listeners.ContextListener

![20201017101626801.png][]

examples应用对于我们读源码影响不大，直接删除调吧。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29ZaW5IZVpoaUd1YW5n_size_16_color_FFFFFF_t_70 7][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29ZaW5IZVpoaUd1YW5n_size_16_color_FFFFFF_t_70 8][]

在如下类中加入相应代码:

//org.apache.catalina.startup.ContextConfig#configureStart
    protected synchronized void configureStart() {
    	// Called from StandardContext.start()
    
    	if (log.isDebugEnabled()) {
    		log.debug(sm.getString("contextConfig.start"));
    	}
    
    	if (log.isDebugEnabled()) {
    		log.debug(sm.getString("contextConfig.xmlSettings",
    				context.getName(),
    				Boolean.valueOf(context.getXmlValidation()),
    				Boolean.valueOf(context.getXmlNamespaceAware())));
    	}
    
    	webConfig();
    
    	//-------------------增加代码 start -------------------------------//
    	context.addServletContainerInitializer(new JasperInitializer(), null);
    	//-------------------增加代码 end -------------------------------//
    	if (!context.getIgnoreAnnotations()) {
    		applicationAnnotationsConfig();
    	}
    	if (ok) {
    		validateSecurityRoles();
    	}
    	...
    }

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