“Default Servlet Reference Table of Contents” 并非一个标准的、由官方（如 Oracle、Apache Tomcat 或 Jakarta EE 规范）

“Default Servlet Reference Table of Contents” 并非一个标准的、由官方如 Oracle、Apache Tomcat 或 Jakarta EE 规范发布的独立文档标题。它通常指Tomcat 服务器中 DefaultServlet 的功能说明与配置参考的目录结构即对 Tomcat 内置的org.apache.catalina.servlets.DefaultServlet负责静态资源服务如 HTML、CSS、JS、图片等的配置项、行为特性、初始化参数及其作用的概览性目录。以下是典型的Tomcat DefaultServlet 参考文档的目录结构Table of ContentsOverview of the Default ServletPurpose and ResponsibilitiesConfiguration in web.xml (or context.xml / server.xml)Initialization Parameters (init-param)-debug-listings目录浏览开关-readonly是否禁止 PUT/DELETE 等写操作-sendfile启用零拷贝传输-fileEncoding/inputEncoding/outputEncoding-useAcceptRanges-welcomeFiles补充默认欢迎页MIME Type Mapping and Resource HandlingCaching Behavior and Cache Control HeadersSecurity Considerations (e.g., path traversal protection, hidden file filtering)Customization via Subclassing or ReplacementCommon Use Cases ExamplesTroubleshooting Logging Tips✅ 注该内容基于 Apache Tomcat 9/10 官方文档DefaultServlet整理Jakarta EE 规范本身不定义 DefaultServlet 实现而是由各 Servlet 容器如 Tomcat、Jetty、WildFly自行提供。!-- 示例在 web.xml 中配置 DefaultServlet通常无需显式配置除非需覆盖默认行为 --servletservlet-namedefault/servlet-nameservlet-classorg.apache.catalina.servlets.DefaultServlet/servlet-classinit-paramparam-namelistings/param-nameparam-valuefalse/param-value/init-paramload-on-startup1/load-on-startup/servletDefault Servlet Reference Table of ContentsWhat is the DefaultServletWhere is it declared?What can I change?How do I customize directory listings?How do I secure directory listings?What is the DefaultServletThe default servlet is the servlet which serves static resources as well as serves the directory listings (if directory listings are enabled).Where is it declared?It is declared globally in $CATALINA_BASE/conf/web.xml. By default here is it’s declaration:servlet servlet-namedefault/servlet-name servlet-class org.apache.catalina.servlets.DefaultServlet /servlet-class init-param param-namedebug/param-name param-value0/param-value /init-param init-param param-namelistings/param-name param-valuefalse/param-value /init-param load-on-startup1/load-on-startup /servlet…servlet-mapping servlet-namedefault/servlet-name url-pattern//url-pattern /servlet-mappingSo by default, the default servlet is loaded at webapp startup and directory listings are disabled and debugging is turned off.What can I change?The DefaultServlet allows the following initParamters:Property Descriptiondebug Debugging level. It is not very useful unless you are a tomcat developer. As of this writing, useful values are 0, 1, 11, 1000. [0]listings If no welcome file is present, can a directory listing be shown? value may be true or false [false]Welcome files are part of the servlet api.WARNING: Listings of directories containing many entries are expensive. Multiple requests for large directory listings can consume significant proportions of server resources.precompressed If a precompressed version of a file exists (a file with .br or .gz appended to the file name located alongside the original file), Tomcat will serve the precompressed file if the user agent supports the matching content encoding (br or gzip) and this option is enabled. [false]The precompressed file with the with .br or .gz extension will be accessible if requested directly so if the original resource is protected with a security constraint, the precompressed versions must be similarly protected.It is also possible to configure the list of precompressed formats. The syntax is comma separated list of [content-encoding][file-extension] pairs. For example: br.br,gzip.gz,bzip2.bz2. If multiple formats are specified, the client supports more than one and the client does not express a preference, the order of the list of formats will be treated as the server preference order and used to select the format returned.readmeFile If a directory listing is presented, a readme file may also be presented with the listing. This file is inserted as is so it may contain HTML.globalXsltFile If you wish to customize your directory listing, you can use an XSL transformation. This value is a relative file name (to either $CATALINA_BASE/conf/ or $CATALINA_HOME/conf/) which will be used for all directory listings. This can be overridden per context and/or per directory. See contextXsltFile and localXsltFile below. The format of the xml is shown below.contextXsltFile You may also customize your directory listing by context by configuring contextXsltFile. This must be a context relative path (e.g.: /path/to/context.xslt) to a file with a .xsl or .xslt extension. This overrides globalXsltFile. If this value is present but a file does not exist, then globalXsltFile will be used. If globalXsltFile does not exist, then the default directory listing will be shown.localXsltFile You may also customize your directory listing by directory by configuring localXsltFile. This must be a file in the directory where the listing will take place to with a .xsl or .xslt extension. This overrides globalXsltFile and contextXsltFile. If this value is present but a file does not exist, then contextXsltFile will be used. If contextXsltFile does not exist, then globalXsltFile will be used. If globalXsltFile does not exist, then the default directory listing will be shown.input Input buffer size (in bytes) when reading resources to be served. [2048]output Output buffer size (in bytes) when writing resources to be served. [2048]readonly Is this context “read only”, so HTTP commands like PUT and DELETE are rejected? [true]fileEncoding File encoding to be used when reading static resources. [platform default]sendfileSize If the connector used supports sendfile, this represents the minimal file size in KB for which sendfile will be used. Use a negative value to always disable sendfile. [48]useAcceptRanges If true, the Accept-Ranges header will be set when appropriate for the response. [true]showServerInfo Should server information be presented in the response sent to clients when directory listing is enabled. [true]sortListings Should the server sort the listings in a directory. [false]sortDirectoriesFirst Should the server list all directories before all files. [false]How do I customize directory listings?You can override DefaultServlet with you own implementation and use that in your web.xml declaration. If you can understand what was just said, we will assume you can read the code to DefaultServlet servlet and make the appropriate adjustments. (If not, then that method isn’t for you)You can use either localXsltFile or globalXsltFile and DefaultServlet will create an xml document and run it through an xsl transformation based on the values provided in localXsltFile and globalXsltFile. localXsltFile is first checked, followed by globalXsltFile, then default behaviors takes place.Format:listing entries entry typefile|dir urlPathaPath size### dategmt date fileName1 /entry entry typefile|dir urlPathaPath size### dategmt date fileName2 /entry ... /entries readme/readme /listing size will be missing if typedir Readme is a CDATA entryThe following is a sample xsl file which mimics the default tomcat behavior:?xml version1.0 encodingUTF-8?xsl:stylesheet xmlns:xsl“http://www.w3.org/1999/XSL/Transform”version“3.0”xsl:output method“html” html-version“5.0”encoding“UTF-8” indent“no”doctype-system“about:legacy-compat”/xsl:template match“listing”Sample Directory Listing ForSample Directory Listing ForFilenameSizeLast ModifiedApache Tomcat/8.5xsl:template match“entries”xsl:apply-templates select“entry”//xsl:templatexsl:template match“readme”xsl:apply-templates//xsl:templatexsl:template match“entry”xsl:variable name“urlPath” select“urlPath”/xsl:apply-templates/xsl:value-of select“size”/xsl:value-of select“date”//xsl:template/xsl:stylesheetHow do I secure directory listings?Use web.xml in each individual webapp. See the security section of the Servlet specification.您可以使用自己的实现重写DefaultServlet并在web.xml声明中使用它。如果您能够理解刚才所说的我们假设您可以将代码读取到DefaultServletServlet并进行适当的调整。如果不是那么这种方法不适合你您可以使用localXsltFile或globalXsltFileDefaultServlet将创建一个xml文档并根据localXsltFile和globalXsltFile中提供的值通过xsl转换运行它。首先检查localXsltFile然后检查globalXsltFile然后执行默认行为。