IDEA运行tomcat8.5.35源代码

前提环境，安装和配置好java1.8+环境，maven，IDEA

1.下载Tomcat源代码：https://tomcat.apache.org/download-80.cgi#8.5.35

2.创建pom.xml

需要通过Maven组织文件，因此需要在apache-tomcat-8.5.35-src根目录下创建目录中新建catalina-home目录和pom.xml文件，如下，

<?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.tomcat</groupId>
    <artifactId>Tomcat8.5</artifactId>
    <name>Tomcat8.5</name>
    <version>8.5</version>

    <build>
        <finalName>Tomcat8.5</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>2.3</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>3.4</version>
        </dependency>
        <dependency>
            <groupId>ant</groupId>
            <artifactId>ant</artifactId>
            <version>1.7.0</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>4.5.1</version>
        </dependency>

    </dependencies>
</project>

apache-tomcat-8.0.53-src目录中的conf和webapps文件夹复制到catalina-home目录中

三、配置IDEA运行项目

Main class设置为org.apache.catalina.startup.Bootstrap

添加VM options

-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

说明：如果编译build的时候出现Test测试代码报错，注释该代码即可。本文中的Tomcat源码util.TestCookieFilter类会报错，将其注释即可

运行项目，访问http://localhost:8080，得到结果：

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中的configureStart函数中手动将JSP解析器初始化：

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();

        context.addServletContainerInitializer(new JasperInitializer(), null);

        if (!context.getIgnoreAnnotations()) {
            applicationAnnotationsConfig();
        }
        if (ok) {
            validateSecurityRoles();
        }

        // Configure an authenticator if we need one
        if (ok) {
            authenticatorConfig();
        }

        // Dump the contents of this pipeline if requested
        if (log.isDebugEnabled()) {
            log.debug("Pipeline Configuration:");
            Pipeline pipeline = context.getPipeline();
            Valve valves[] = null;
            if (pipeline != null) {
                valves = pipeline.getValves();
            }
            if (valves != null) {
                for (int i = 0; i < valves.length; i++) {
                    log.debug("  " + valves[i].getClass().getName());
                }
            }
            log.debug("======================");
        }

        // Make our application available if no problems were encountered
        if (ok) {
            context.setConfigured(true);
        } else {
            log.error(sm.getString("contextConfig.unavailable"));
            context.setConfigured(false);
        }

    }

修改完后，项目再启动，我们再在浏览器访问http://localhost:8080/ ，就可以看到我们所熟悉的经典欢迎页面了