• Tomcat 源码分析 (Digester类的使用) (十)

    文章目录

    1.Digester 类的介绍

    apache的Digester库是专门用解析管理xml文档，在tomcat中也使用了这个第三方类库来解析xml文档，也就是对应的server.xml和web.xml

    org.apache.commons.digester.Digester类是Digester库的主类，该类可以用来解析xml文档，对于xml文档中的每个元素，Digester对象都会检查他事先预定义的事件。在调用Digester对象parse()方法之前，需要预先定义事件来完成解析。

    2.Digester 类的使用

    在之前的tomcat启动过程源码讲解的时候，我们讲过Catalina类实例的load()

    Catalina,load()

    在这里插入图片描述

    在这里插入图片描述

        protected Digester createStartDigester() {
        // Initialize the digester
        Digester digester = new Digester();
        digester.setValidating(false);
        digester.setRulesValidation(true);
        Map<Class<?>, List<String>> fakeAttributes = new HashMap<>();
        // Ignore className on all elements
        List<String> objectAttrs = new ArrayList<>();
        objectAttrs.add("className");
        fakeAttributes.put(Object.class, objectAttrs);
        // Ignore attribute added by Eclipse for its internal tracking
        List<String> contextAttrs = new ArrayList<>();
        contextAttrs.add("source");
        fakeAttributes.put(StandardContext.class, contextAttrs);
        // Ignore Connector attribute used internally but set on Server
        List<String> connectorAttrs = new ArrayList<>();
        connectorAttrs.add("portOffset");
        fakeAttributes.put(Connector.class, connectorAttrs);
        digester.setFakeAttributes(fakeAttributes);
        digester.setUseContextClassLoader(true);

        // Configure the actions we will be using
        // 根据Server标签创建Server对象，实例是StandardServer,设置属性，并且调用前一个对象的setServer方法，将StandardServer对象设置进去
        digester.addObjectCreate("Server",
                                 "org.apache.catalina.core.StandardServer",
                                 "className");
        digester.addSetProperties("Server");
        digester.addSetNext("Server",
                            "setServer",
                            "org.apache.catalina.Server");

        digester.addObjectCreate("Server/GlobalNamingResources",
                                 "org.apache.catalina.deploy.NamingResourcesImpl");
        digester.addSetProperties("Server/GlobalNamingResources");
        digester.addSetNext("Server/GlobalNamingResources",
                            "setGlobalNamingResources",
                            "org.apache.catalina.deploy.NamingResourcesImpl");
		
		// 遇到Listener标签，根据标签上className属性上类创建对应的对象，设置对应Listener的属性并且将该对象设置到StandardServer中
        digester.addRule("Server/Listener",
                new ListenerCreateRule(null, "className"));
        digester.addSetProperties("Server/Listener");
        digester.addSetNext("Server/Listener",
                            "addLifecycleListener",
                            "org.apache.catalina.LifecycleListener");

		// 遇到Service标签创建StandardService对象，然后设置其属性，然后将StandardService实例设置到StandardServer中
        digester.addObjectCreate("Server/Service",
                                 "org.apache.catalina.core.StandardService",
                                 "className");
        digester.addSetProperties("Server/Service");
        digester.addSetNext("Server/Service",
                            "addService",
                            "org.apache.catalina.Service");

		// 遇到Service标签内部的Listener标签，跟上面一样创建对应的listener对象，然后设置到 StandardService对象中。
        digester.addObjectCreate("Server/Service/Listener",
                                 null, // MUST be specified in the element
                                 "className");
        digester.addSetProperties("Server/Service/Listener");
        digester.addSetNext("Server/Service/Listener",
                            "addLifecycleListener",
                            "org.apache.catalina.LifecycleListener");

        //Executor
        // 创建对应的Executor 然后设置到StandardService中
        digester.addObjectCreate("Server/Service/Executor",
                         "org.apache.catalina.core.StandardThreadExecutor",
                         "className");
        digester.addSetProperties("Server/Service/Executor");

        digester.addSetNext("Server/Service/Executor",
                            "addExecutor",
                            "org.apache.catalina.Executor");

        digester.addRule("Server/Service/Connector",
                         new ConnectorCreateRule());
        digester.addSetProperties("Server/Service/Connector",
                new String[]{"executor", "sslImplementationName", "protocol"});
		// 将Connecter实例添加到 StandardService中                
        digester.addSetNext("Server/Service/Connector",
                            "addConnector",
                            "org.apache.catalina.connector.Connector");

        digester.addRule("Server/Service/Connector", new AddPortOffsetRule());

        digester.addObjectCreate("Server/Service/Connector/SSLHostConfig",
                                 "org.apache.tomcat.util.net.SSLHostConfig");
        digester.addSetProperties("Server/Service/Connector/SSLHostConfig");
        digester.addSetNext("Server/Service/Connector/SSLHostConfig",
                "addSslHostConfig",
                "org.apache.tomcat.util.net.SSLHostConfig");

        digester.addRule("Server/Service/Connector/SSLHostConfig/Certificate",
                         new CertificateCreateRule());
        digester.addSetProperties("Server/Service/Connector/SSLHostConfig/Certificate", new String[]{"type"});
        digester.addSetNext("Server/Service/Connector/SSLHostConfig/Certificate",
                            "addCertificate",
                            "org.apache.tomcat.util.net.SSLHostConfigCertificate");

        digester.addObjectCreate("Server/Service/Connector/SSLHostConfig/OpenSSLConf",
                                 "org.apache.tomcat.util.net.openssl.OpenSSLConf");
        digester.addSetProperties("Server/Service/Connector/SSLHostConfig/OpenSSLConf");
        digester.addSetNext("Server/Service/Connector/SSLHostConfig/OpenSSLConf",
                            "setOpenSslConf",
                            "org.apache.tomcat.util.net.openssl.OpenSSLConf");

        digester.addObjectCreate("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd",
                                 "org.apache.tomcat.util.net.openssl.OpenSSLConfCmd");
        digester.addSetProperties("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd");
        digester.addSetNext("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd",
                            "addCmd",
                            "org.apache.tomcat.util.net.openssl.OpenSSLConfCmd");

        digester.addObjectCreate("Server/Service/Connector/Listener",
                                 null, // MUST be specified in the element
                                 "className");
        // 创建Connector 内部的listener
        digester.addSetProperties("Server/Service/Connector/Listener");
        digester.addSetNext("Server/Service/Connector/Listener",
                            "addLifecycleListener",
                            "org.apache.catalina.LifecycleListener");

        digester.addObjectCreate("Server/Service/Connector/UpgradeProtocol",
                                  null, // MUST be specified in the element
                                  "className");
        digester.addSetProperties("Server/Service/Connector/UpgradeProtocol");
        digester.addSetNext("Server/Service/Connector/UpgradeProtocol",
                            "addUpgradeProtocol",
                            "org.apache.coyote.UpgradeProtocol");

        // Add RuleSets for nested elements
        digester.addRuleSet(new NamingRuleSet("Server/GlobalNamingResources/"));
        digester.addRuleSet(new EngineRuleSet("Server/Service/"));
        digester.addRuleSet(new HostRuleSet("Server/Service/Engine/"));
        digester.addRuleSet(new ContextRuleSet("Server/Service/Engine/Host/"));
        addClusterRuleSet(digester, "Server/Service/Engine/Host/Cluster/");
        digester.addRuleSet(new NamingRuleSet("Server/Service/Engine/Host/Context/"));

        // When the 'engine' is found, set the parentClassLoader.
        digester.addRule("Server/Service/Engine",
                         new SetParentClassLoaderRule(parentClassLoader));
        addClusterRuleSet(digester, "Server/Service/Engine/Cluster/");

        return digester;

    }

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    创建对象

    public void addObjectCreate(String pattern, String className)
public void addObjectCreate(String pattern, Class clazz)
public void addObjectCreate(String pattern, String className,String attributeName)
public void addObjectCreate(String pattern,String attributeName,Class clazz)

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    设置属性

    public void addSetProperties(String pattern) 
public void addSetProperties(String pattern,String attributeName,String propertyName) 
public void addSetProperties(String pattern,String [] attributeNames,String [] propertyNames)
public void addSetProperty(String pattern, String name, String value)

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    调用方法

    public void addCallMethod(String pattern, String methodName)

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    创建对象之间的关系

    public void addSetNext(String pattern, String methodName)
public void addSetNext(String pattern, String methodName,String paramType)

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    向Digester类中再添加规则

    public void addRuleSet(RuleSet ruleSet)

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    3.Rule相关类

    • Rule
    • RuleBase
    • RuleSet

    Rule.java

    Rule类也是Digester中比较重要的类，包含了一些常用的方法，比如begin(),body(),end()等，当Digester对象解析到标签开始的时候会调用begin()方法，到标签内会调用body()方法，在标签末位的时候会调用end()方法。我们可以查看下addObjectCreate方法看看，该方法如何实现。

    在这里插入图片描述

        public void addRule(String pattern, Rule rule) {

        rule.setDigester(this);
        getRules().add(pattern, rule);

    }

    public Rules getRules() {
        if (this.rules == null) {
            this.rules = new RulesBase();
            this.rules.setDigester(this);
        }
        return this.rules;
    }

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    addRule是往Digester内部的一个对象rules中添加了一条rule，而其中rules指向的是一个RuleBase对象

    RuleBase.java

    RuleBase代表Digester类包含的所有规则集合, RuleBase内部有个HashMap存放着所有的规则，map的key是匹配规则，值是该规则对应的所有Rule的集合。

    在这里插入图片描述

        @Override
    public void add(String pattern, Rule rule) {
        // to help users who accidentally add '/' to the end of their patterns
        int patternLength = pattern.length();
        if (patternLength>1 && pattern.endsWith("/")) {
            pattern = pattern.substring(0, patternLength-1);
        }

        List<Rule> list = cache.get(pattern);
        if (list == null) {
            list = new ArrayList<>();
            cache.put(pattern, list);
        }
        list.add(rule);
        rules.add(rule);
        if (this.digester != null) {
            rule.setDigester(this.digester);
        }
    }

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    ConnectorCreateRule.java

    继承了Rule对象，复写了begin方法

        @Override
    public void begin(String namespace, String name, Attributes attributes)
            throws Exception {
        Service svc = (Service) digester.peek();
        Executor ex = null;
        String executorName = attributes.getValue("executor");
        if (executorName != null ) {
            ex = svc.getExecutor(executorName);
        }
        String protocolName = attributes.getValue("protocol");
        Connector con = new Connector(protocolName);
        if (ex != null) {
            setExecutor(con, ex);
        }
        String sslImplementationName = attributes.getValue("sslImplementationName");
        if (sslImplementationName != null) {
            setSSLImplementationName(con, sslImplementationName);
        }
        digester.push(con);

        StringBuilder code = digester.getGeneratedCode();
        if (code != null) {
            code.append(System.lineSeparator());
            code.append(Connector.class.getName()).append(' ').append(digester.toVariableName(con));
            code.append(" = new ").append(Connector.class.getName());
            code.append("(new ").append(con.getProtocolHandlerClassName()).append("());");
            code.append(System.lineSeparator());
            if (ex != null) {
                code.append(digester.toVariableName(con)).append(".getProtocolHandler().setExecutor(");
                code.append(digester.toVariableName(svc)).append(".getExecutor(").append(executorName);
                code.append("));");
                code.append(System.lineSeparator());
            }
            if (sslImplementationName != null) {
                code.append("((").append(AbstractHttp11JsseProtocol.class.getName()).append(") ");
                code.append(digester.toVariableName(con)).append(".getProtocolHandler()).setSslImplementationName(\"");
                code.append(sslImplementationName).append("\");");
                code.append(System.lineSeparator());
            }
        }
    }

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    RuleSet.java

    在这里插入图片描述

    实现类

    在这里插入图片描述
    EngineRuleSet.addRuleInstances()

        @Override
    public void addRuleInstances(Digester digester) {

        digester.addObjectCreate(prefix + "Engine",
                                 "org.apache.catalina.core.StandardEngine",
                                 "className");
        digester.addSetProperties(prefix + "Engine");
        digester.addRule(prefix + "Engine",
                         new LifecycleListenerRule
                         ("org.apache.catalina.startup.EngineConfig",
                          "engineConfigClass"));
        digester.addSetNext(prefix + "Engine",
                            "setContainer",
                            "org.apache.catalina.Engine");

        //Cluster configuration start
        digester.addObjectCreate(prefix + "Engine/Cluster",
                                 null, // MUST be specified in the element
                                 "className");
        digester.addSetProperties(prefix + "Engine/Cluster");
        digester.addSetNext(prefix + "Engine/Cluster",
                            "setCluster",
                            "org.apache.catalina.Cluster");
        //Cluster configuration end

        digester.addObjectCreate(prefix + "Engine/Listener",
                                 null, // MUST be specified in the element
                                 "className");
        digester.addSetProperties(prefix + "Engine/Listener");
        digester.addSetNext(prefix + "Engine/Listener",
                            "addLifecycleListener",
                            "org.apache.catalina.LifecycleListener");


        digester.addRuleSet(new RealmRuleSet(prefix + "Engine/"));

        digester.addObjectCreate(prefix + "Engine/Valve",
                                 null, // MUST be specified in the element
                                 "className");
        digester.addSetProperties(prefix + "Engine/Valve");
        digester.addSetNext(prefix + "Engine/Valve",
                            "addValve",
                            "org.apache.catalina.Valve");
    }

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    完善创建StandardEngine对象并且设置内部各种属性和对象的引用。

    HostRuleSet,ContextRuleSet 差不多

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  • 原文地址：https://blog.csdn.net/qq_43141726/article/details/126038075