struts1源碼學習2（initChain）

標籤：java digester xml xml解析 initchain

先上代碼

protected void initChain()        throws ServletException {        // Parse the configuration file specified by path or resource        try {        //還是先從servlet配置中找chainConfig        //預設值是chainConfig = "org/apache/struts/chain/chain-config.xml";            String value;            value = getServletConfig().getInitParameter("chainConfig");            if (value != null) {                chainConfig = value;            }            ConfigParser parser = new ConfigParser();            List urls = splitAndResolvePaths(chainConfig);            URL resource;            for (Iterator i = urls.iterator(); i.hasNext();) {                resource = (URL) i.next();                log.info("Loading chain catalog from " + resource);                parser.parse(resource);            }        } catch (Exception e) {            log.error("Exception loading resources", e);            throw new ServletException(e);        }    }

這段代碼比較少，也比較簡單，就是解析chain-config.xml檔案。（如果是多個檔案，中間逗號分隔）

但是這個檔案對struts的意義暫時還不是很清楚。（看字面的話，貌似是命令鏈條，用的裝飾器模式？）

chain-config.xml檔案

<?xml version="1.0" ?><catalog name="struts">    <define name="lookup"            className="org.apache.commons.chain.generic.LookupCommand"/>    <!-- ========== Servlet Complete Request Chain ========================= -->    <chain name="servlet-standard">        <!-- Establish exception handling filter -->        <command                className="org.apache.struts.chain.commands.ExceptionCatcher"                catalogName="struts"                exceptionCommand="servlet-exception"/>        <lookup                catalogName="struts"                name="process-action"                optional="false"/>        <lookup                catalogName="struts"                name="process-view"                optional="false"/>    </chain>    <!-- ========== Action Processing chain ======================== -->    <chain name="process-action">        <!-- Look up optional preprocess command -->        <lookup                catalogName="struts"                name="servlet-standard-preprocess"                optional="true"/>        <command                className="org.apache.struts.chain.commands.servlet.SelectLocale"/>        <command                className="org.apache.struts.chain.commands.servlet.SetOriginalURI"/>        <command                className="org.apache.struts.chain.commands.servlet.RequestNoCache"/>        <command                className="org.apache.struts.chain.commands.servlet.SetContentType"/>        <command                className="org.apache.struts.chain.commands.RemoveCachedMessages"/>        <command                className="org.apache.struts.chain.commands.servlet.SelectAction"/>        <command                className="org.apache.struts.chain.commands.servlet.AuthorizeAction"/>        <command                className="org.apache.struts.chain.commands.CreateActionForm"/>        <command                className="org.apache.struts.chain.commands.servlet.PopulateActionForm"/>        <command                className="org.apache.struts.chain.commands.servlet.ValidateActionForm"/>        <command                className="org.apache.struts.chain.commands.servlet.SelectInput"/>        <command                className="org.apache.struts.chain.commands.ExecuteCommand"/>        <command                className="org.apache.struts.chain.commands.servlet.SelectForward"/>        <command                className="org.apache.struts.chain.commands.SelectInclude"/>        <command                className="org.apache.struts.chain.commands.servlet.PerformInclude"/>        <command                className="org.apache.struts.chain.commands.servlet.CreateAction"/>        <command                className="org.apache.struts.chain.commands.servlet.ExecuteAction"/>    </chain>    <!-- ========== View Processing chain ======================== -->    <chain name="process-view">        <command                className="org.apache.struts.chain.commands.ExecuteForwardCommand"/>        <command                className="org.apache.struts.chain.commands.servlet.PerformForward"/>    </chain>    <chain name="servlet-exception">        <command                className="org.apache.struts.chain.commands.servlet.ExceptionHandler"/>        <command                className="org.apache.struts.chain.commands.servlet.PerformForward"/>    </chain></catalog>

目測還是要從

ConfigParser

這個類入手

public class ConfigParser {    private Digester digester = null;    private RuleSet ruleSet = null;    private boolean useContextClassLoader = true;    public Digester getDigester() {        if (digester == null) {            digester = new Digester();            RuleSet ruleSet = getRuleSet();            digester.setNamespaceAware(ruleSet.getNamespaceURI() != null);            digester.setUseContextClassLoader(getUseContextClassLoader());            digester.setValidating(false);            digester.addRuleSet(ruleSet);        }        return (digester);    }    public RuleSet getRuleSet() {        if (ruleSet == null) {            ruleSet = new ConfigRuleSet();        }        return (ruleSet);    }    public void setRuleSet(RuleSet ruleSet) {        this.digester = null;        this.ruleSet = ruleSet;    }    public boolean getUseContextClassLoader() {        return (this.useContextClassLoader);    }    public void setUseContextClassLoader(boolean useContextClassLoader) {        this.useContextClassLoader = useContextClassLoader;    }    public void parse(Catalog catalog, URL url) throws Exception {        Digester digester = getDigester();        digester.clear();        digester.push(catalog);        digester.parse(url);    }    public void parse(URL url) throws Exception {        Digester digester = getDigester();        digester.clear();        digester.parse(url);    }}

直接找到parse方法，好吧，三行，再看getDigester方法，好，裡面出現了RuleSet，目測解析就在這個

ConfigRuleSet裡面。

ConfigRuleSet代碼（各種setget被我去掉了）

public class ConfigRuleSet extends RuleSetBase {//貌似是分類、鏈條類？className也出現了，估計就是這裡    private String catalogClass = "org.apache.commons.chain.impl.CatalogBase";    private String catalogElement = "catalog";    private String chainClass = "org.apache.commons.chain.impl.ChainBase";    private String chainElement = "chain";    private String classAttribute = "className";    private String commandElement = "command";    private String defineElement = "define";    private String nameAttribute = "name";    public void addRuleInstances(Digester digester) {        // catalog用ConfigCatalogRule處理,並且將成功處理的catalog放入CatalogFactory的一個map中，此map的key是catalog的classloader        digester.addRule("*/" + getCatalogElement(),                         new ConfigCatalogRule(nameAttribute, catalogClass));        digester.addSetProperties("*/" + getCatalogElement());        //以下都是解析catalog的代碼        // 建立org.apache.commons.chain.impl.ChainBase這個類        //解析chain,三個參數，第一個是匹配運算式，第二個是預設建立類名稱，第三個是當匹配運算式所在的屬性來作為類名        digester.addObjectCreate("*/" + getChainElement(),                                 getChainClass(),                                 getClassAttribute());        digester.addSetProperties("*/" + getChainElement());        //規則ConfigRegisterRule        digester.addRule("*/" + getChainElement(),                         new ConfigRegisterRule(nameAttribute));        // Add rules for a command element        digester.addObjectCreate("*/" + getCommandElement(),                                 null,                                 getClassAttribute());        digester.addSetProperties("*/" + getCommandElement());        digester.addRule("*/" + getCommandElement(),                         new ConfigRegisterRule(nameAttribute));        // Add rules for a define element        digester.addRule("*/" + getDefineElement(),                         new ConfigDefineRule(getNameAttribute(),                                              getClassAttribute()));    }}

CatalogFactory將解析後的catalog放入自身map，留作後續使用

本文出自 “helloworld” 部落格，請務必保留此出處http://lawrence16.blog.51cto.com/1908331/1532036