spring-boot-2.0.3源码篇 - filter的注册，值得一看
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开心一刻
过年女婿来岳父家走亲戚
当时小舅子主就问：姐夫，你什么时候能给我姐幸福，让我姐好好享受生活的美好。你们这辈子不准备买一套大点的房子吗？
姐夫说：现在没钱啊！不过我有一个美丽可爱的女儿，等长大后找个有钱的老公嫁了，那时我就能和你姐一起住大房子了
岳父不乐意的说了一句：当初我也是这么认为的，可惜未能如愿
ServletContext
ServletContext介绍
定义了servlet与其servlet容器通信的一些列方法，例如，获取文件的MIME类型，分派请求或写入日志文件。
Servlet的运行模式是一个典型的“握手型的交互式”运行模式。所谓“握手型的交互式”就是两个模块为了交换数据通常都会准备一个交易场景，这个场景一直跟随这个交易过程直到这个交易完成为止。这个交易场景的初始化是根据这次交易对象指定的参数来定制的，这些制定参数通常就是一个配置类。所以对号入座，交易场景由ServletContext来描述，而定制的参数集合由ServletConfig来描述。而ServletRequest和ServletResponse就是要交互的具体对象，它们通常都作为运输工具来传递交互结果。ServletContext，即servlet上下文，用于存放web应用信息；每个Java虚拟机每个Web项目只有一个ServletContext，它是由Web服务器创建，代表当前web应用。
Servlet 3.0规范之前
我们采用2.5来看下源码
maven依赖
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
<scope>provided</scope>
</dependency>
源码
/* * The contents of this file are subject to the terms * of the Common Development and Distribution License * (the "License"). You may not use this file except * in compliance with the License. * * You can obtain a copy of the license at * glassfish/bootstrap/legal/CDDLv1.0.txt or * https://glassfish.dev.java.net/public/CDDLv1.0.html. * See the License for the specific language governing * permissions and limitations under the License. * * When distributing Covered Code, include this CDDL * HEADER in each file and include the License file at * glassfish/bootstrap/legal/CDDLv1.0.txt. If applicable, * add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your * own identifying information: Portions Copyright [yyyy] * [name of copyright owner] * * Copyright 2005 Sun Microsystems, Inc. All rights reserved. * * Portions Copyright Apache Software Foundation. */ package javax.servlet; import java.io.InputStream; import java.net.MalformedURLException; import java.net.URL; import java.util.Enumeration; import java.util.Set; /** * * Defines a set of methods that a servlet uses to communicate with its * servlet container, for example, to get the MIME type of a file, dispatch * requests, or write to a log file. * * <p>There is one context per "web application" per Java Virtual Machine. (A * "web application" is a collection of servlets and content installed under a * specific subset of the server\'s URL namespace such as <code>/catalog</code> * and possibly installed via a <code>.war</code> file.) * * <p>In the case of a web * application marked "distributed" in its deployment descriptor, there will * be one context instance for each virtual machine. In this situation, the * context cannot be used as a location to share global information (because * the information won\'t be truly global). Use an external resource like * a database instead. * * <p>The <code>ServletContext</code> object is contained within * the {@link ServletConfig} object, which the Web server provides the * servlet when the servlet is initialized. * * @author Various * * @see Servlet#getServletConfig * @see ServletConfig#getServletContext * */ public interface ServletContext { /** * Returns the context path of the web application. * * <p>The context path is the portion of the request URI that is used * to select the context of the request. The context path always comes * first in a request URI. The path starts with a "/" character but does * not end with a "/" character. For servlets in the default (root) * context, this method returns "". * * <p>It is possible that a servlet container may match a context by * more than one context path. In such cases the * {@link javax.servlet.http.HttpServletRequest#getContextPath()} * will return the actual context path used by the request and it may * differ from the path returned by this method. * The context path returned by this method should be considered as the * prime or preferred context path of the application. * * @return The context path of the web application, or "" for the * default (root) context * * @see javax.servlet.http.HttpServletRequest#getContextPath() * * @since Servlet 2.5 */ public String getContextPath(); /** * Returns a <code>ServletContext</code> object that * corresponds to a specified URL on the server. * * <p>This method allows servlets to gain * access to the context for various parts of the server, and as * needed obtain {@link RequestDispatcher} objects from the context. * The given path must be begin with "/", is interpreted relative * to the server\'s document root and is matched against the context roots of * other web applications hosted on this container. * * <p>In a security conscious environment, the servlet container may * return <code>null</code> for a given URL. * * @param uripath a <code>String</code> specifying the context path of * another web application in the container. * @return the <code>ServletContext</code> object that * corresponds to the named URL, or null if either none exists or the container wishes to restrict * this access. * * @see RequestDispatcher * */ public ServletContext getContext(String uripath); /** * Returns the major version of the Java Servlet API that this * servlet container supports. All implementations that comply * with Version 2.5 must have this method * return the integer 2. * * @return 2 * */ public int getMajorVersion(); /** * Returns the minor version of the Servlet API that this * servlet container supports. All implementations that comply * with Version 2.5 must have this method * return the integer 5. * * @return 5 * */ public int getMinorVersion(); /** * Returns the MIME type of the specified file, or <code>null</code> if * the MIME type is not known. The MIME type is determined * by the configuration of the servlet container, and may be specified * in a web application deployment descriptor. Common MIME * types are <code>"text/html"</code> and <code>"image/gif"</code>. * * * @param file a <code>String</code> specifying the name * of a file * * @return a <code>String</code> specifying the file\'s MIME type * */ public String getMimeType(String file); /** * Returns a directory-like listing of all the paths to resources within the web application whose longest sub-path * matches the supplied path argument. Paths indicating subdirectory paths end with a \'/\'. The returned paths are all * relative to the root of the web application and have a leading \'/\'. For example, for a web application * containing<br><br> * /welcome.html<br> * /catalog/index.html<br> * /catalog/products.html<br> * /catalog/offers/books.html<br> * /catalog/offers/music.html<br> * /customer/login.jsp<br> * /WEB-INF/web.xml<br> * /WEB-INF/classes/com.acme.OrderServlet.class,<br><br> * * getResourcePaths("/") returns {"/welcome.html", "/catalog/", "/customer/", "/WEB-INF/"}<br> * getResourcePaths("/catalog/") returns {"/catalog/index.html", "/catalog/products.html", "/catalog/offers/"}.<br> *@param path the partial path used to match the resources, * which must start with a / *@return a Set containing the directory listing, or null if there are no resources in the web application whose path * begins with the supplied path. * @since Servlet 2.3 */ public Set getResourcePaths(String path); /** * Returns a URL to the resource that is mapped to a specified * path. The path must begin with a "/" and is interpreted * as relative to the current context root. * * <p>This method allows the servlet container to make a resource * available to servlets from any source. Resources * can be located on a local or remote * file system, in a database, or in a <code>.war</code> file. * * <p>The servlet container must implement the URL handlers * and <code>URLConnection</code> objects that are necessary * to access the resource. * * <p>This method returns <code>null</code> * if no resource is mapped to the pathname. * * <p>Some containers may allow writing to the URL returned by * this method using the methods of the URL class. * * <p>The resource content is returned directly, so be aware that * requesting a <code>.jsp</code> page returns the JSP source code. * Use a <code>RequestDispatcher</code> instead to include results of * an execution. * * <p>This method has a different purpose than * <code>java.lang.Class.getResource</code>, * which looks up resources based on a class loader. This * method does not use class loaders. * * @param path a <code>String</code> specifying * the path to the resource * * @return the resource located at the named path, * or <code>null</code> if there is no resource * at that path * * @exception MalformedURLException if the pathname is not given in * the correct form * */ public URL getResource(String path) throws MalformedURLException; /** * Returns the resource located at the named path as * an <code>InputStream</code> object. * * <p>The data in the <code>InputStream</code> can be * of any type or length. The path must be specified according * to the rules given in <code>getResource</code>. * This method returns <code>null</code> if no resource exists at * the specified path. * * <p>Meta-information such as content length and content type * that is available via <code>getResource</code> * method is lost when using this method. * * <p>The servlet container must implement the URL handlers * and <code>URLConnection</code> objects necessary to access * the resource. * * <p>This method is different from * <code>java.lang.Class.getResourceAsStream</code>, * which uses a class loader. This method allows servlet containers * to make a resource available * to a servlet from any location, without using a class loader. * * * @param path a <code>String</code> specifying the path * to the resource * * @return the <code>InputStream</code> returned to the * servlet, or <code>null</code> if no resource * exists at the specified path * * */ public InputStream getResourceAsStream(String path); /** * * Returns a {@link RequestDispatcher} object that acts * as a wrapper for the resource located at the given path. * A <code>RequestDispatcher</code> object can be used to forward * a request to the resource or to include the resource in a response. * The resource can be dynamic or static. * * <p>The pathname must begin with a "/" and is interpreted as relative * to the current context root. Use <code>getContext</code> to obtain * a <code>RequestDispatcher</code> for resources in foreign contexts. * This method returns <code>null</code> if the <code>ServletContext</code> * cannot return a <code>RequestDispatcher</code>. * * @param path a <code>String</code> specifying the pathname * to the resource * * @return a <code>RequestDispatcher</code> object * that acts as a wrapper for the resource * at the specified path, or <code>null</code> if * the <code>ServletContext</code> cannot return * a <code>RequestDispatcher</code> * * @see RequestDispatcher * @see ServletContext#getContext * */ public RequestDispatcher getRequestDispatcher(String path); /** * Returns a {@link RequestDispatcher} object that acts * as a wrapper for the named servlet. * * <p>Servlets (and JSP pages also) may be given names via server * administration or via a web application deployment descriptor. * A servlet instance can determine its name using * {@link ServletConfig#getServletName}. * * <p>This method returns <code>null</code> if the * <code>ServletContext</code> * cannot return a <code>RequestDispatcher</code> for any reason. * * @param name a <code>String</code> specifying the name * of a servlet to wrap * * @return a <code>RequestDispatcher</code> object * that acts as a wrapper for the named servlet, * or <code>null</code> if the <code>ServletContext</code> * cannot return a <code>RequestDispatcher</code> * * @see RequestDispatcher * @see ServletContext#getContext * @see ServletConfig#getServletName * */ public RequestDispatcher getNamedDispatcher(String name); /** * * @deprecated As of Java Servlet API 2.1, with no direct replacement. * * <p>This method was originally defined to retrieve a servlet * from a <code>ServletContext</code>. In this version, this method * always returns <code>null</code> and remains only to preserve * binary compatibility. This method will be permanently removed * in a future version of the Java Servlet API. * * <p>In lieu of this method, servlets can share information using the * <code>ServletContext</code> class and can perform shared business logic * by invoking methods on common non-servlet classes. * */ public Servlet getServlet(String name) throws ServletException; /** * * @deprecated As of Java Servlet API 2.0, with no replacement. * * <p>This method was originally defined to return an <code>Enumeration</code> * of all the servlets known to this servlet context. In this * version, this method always returns an empty enumeration and * remains only to preserve binary compatibility. This method * will be permanently removed in a future version of the Java * Servlet API. * */ public Enumeration getServlets(); /** * @deprecated As of Java Servlet API 2.1, with no replacement. * * <p>This method was originally defined to return an * <code>Enumeration</code> * of all the servlet names known to this context. In this version, * this method always returns an empty <code>Enumeration</code> and * remains only to preserve binary compatibility. This method will * be permanently removed in a future version of the Java Servlet API. * */ public Enumeration getServletNames(); /** * * Writes the specified message to a servlet log file, usually * an event log. The name and type of the servlet log file is * specific to the servlet container. * * * @param msg a <code>String</code> specifying the * message to be written to the log file * */ public void log(String msg); /** * @deprecated As of Java Servlet API 2.1, use * {@link #log(String message, Throwable throwable)} * instead. * * <p>This method was originally defined to write an * exception\'s stack trace and an explanatory error message * to the servlet log file. * */ public void log(Exception exception, String msg); /** * Writes an explanatory message and a stack trace * for a given <code>Throwable</code> exception * to the servlet log file. The name and type of the servlet log * file is specific to the servlet container, usually an event log. * * * @param message a <code>String</code> that * describes the error or exception * * @param throwable the <code>Throwable</code> error * or exception * */ public void log(String message, Throwable throwable); /** * Returns a <code>String</code> containing the real path * for a given virtual path. For example, the path "/index.html" * returns the absolute file path on the server\'s filesystem would be * served by a request for "http://host/contextPath/index.html", * where contextPath is the context path of this ServletContext.. * * <p>The real path returned will be in a form * appropriate to the computer and operating system on * which the servlet container is running, including the * proper path separators. This method returns <code>null</code> * if the servlet container cannot translate the virtual path * to a real path for any reason (such as when the content is * being made available from a <code>.war</code> archive). * * * @param path a <code>String</code> specifying a virtual path * * * @return a <code>String</code> specifying the real path, * or null if the translation cannot be performed * * */ public String getRealPath(String path); /** * Returns the name and version of the servlet container on which * the servlet is running. * * <p>The form of the returned string is * <i>servername</i>/<i>versionnumber</i>. * For example, the JavaServer Web Development Kit may return the string * <code>JavaServer Web Dev Kit/1.0</code>. * * <p>The servlet container may return other optional information * after the primary string in parentheses, for example, * <code>JavaServer Web Dev Kit/1.0 (JDK 1.1.6; Windows NT 4.0 x86)</code>. * * * @return a <code>String</code> containing at least the * servlet container name and version number * */ public String getServerInfo(); /** * Returns a <code>String</code> containing the value of the named * context-wide initialization parameter, or <code>null</code> if the * parameter does not exist. * * <p>This method can make available configuration information useful * to an entire "web application". For example, it can provide a * webmaster\'s email address or the name of a system that holds * critical data. * * @param name a <code>String</code> containing the name of the * parameter whose value is requested * * @return a <code>String</code> containing at least the * servlet container name and version number * * @see ServletConfig#getInitParameter */ public String getInitParameter(String name); /** * Returns the names of the context\'s initialization parameters as an * <code>Enumeration</code> of <code>String</code> objects, or an * empty <code>Enumeration</code> if the context has no initialization * parameters. * * @return an <code>Enumeration</code> of <code>String</code> * objects containing the names of the context\'s * initialization parameters * * @see ServletConfig#getInitParameter */ public Enumeration getInitParameterNames(); /** * Returns the servlet container attribute with the given name, * or <code>null</code> if there is no attribute by that name. * An attribute allows a servlet container to give the * servlet additional information not * already provided by this interface. See your * server documentation for information about its attributes. * A list of supported attributes can be retrieved using * <code>getAttributeNames</code>. * * <p>The attribute is returned as a <code>java.lang.Object</code> * or some subclass. * Attribute names should follow the same convention as package * names. The Java Servlet API specification reserves names * matching <code>java.*</code>, <code>javax.*</code>, * and <code>sun.*</code>. * * * @param name a <code>String</code> specifying the name * of the attribute * * @return an <code>Object</code> containing the value * of the attribute, or <code>null</code> * if no attribute exists matching the given * name * * @see ServletContext#getAttributeNames * */ public Object getAttribute(String name); /** * Returns an <code>Enumeration</code> containing the * attribute names available * within this servlet context. Use the * {@link #getAttribute} method with an attribute name * to get the value of an attribute. * * @return an <code>Enumeration</code> of attribute * names * * @see #getAttribute * */ public Enumeration getAttributeNames(); /** * * Binds an object to a given attribute name in this servlet context. If * the name specified is already used for an attribute, this * method will replace the attribute with the new to the new attribute. * <p>If listeners are configured on the <code>ServletContext</code> the * container notifies them accordingly. * <p> * If a null value is passed, the effect is the same as calling * <code>removeAttribute()</code>. * * <p>Attribute names should follow the same convention as package * names. The Java Servlet API specification reserves names * matching <code>java.*</code>, <code>javax.*</code>, and * <code>sun.*</code>. * * * @param name a <code>String</code> specifying the name * of the attribute * * @param object an <code>Object</code> representing the * attribute to be bound * * * */ public void setAttribute(String name, Object object); /** * Removes the attribute with the given name from * the servlet context. After removal, subsequent calls to * {@link #getAttribute} to retrieve the attribute\'s value * will return <code>null</code>. * <p>If listeners are configured on the <code>ServletContext</code> the * container notifies them accordingly. * * * @param name a <code>String</code> specifying the name * of the attribute to be removed * */ public void removeAttribute(String name); /** * Returns the name of this web application corresponding to this ServletContext as specified in the deployment * descriptor for this web application by the display-name element. * * * @return The name of the web application or null if no name has been declared in the deployment descriptor. * @since Servlet 2.3 */ public String getServletContextName(); }
定义了 一些列的方法，具体就不看了，有兴趣的可以详细看下
Servlet 3.0+ 规范
我们采用4.0.1来看下源码
maven依赖
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>provided</scope>
</dependency>
源码
/* * Copyright (c) 1997-2018 Oracle and/or its affiliates. All rights reserved. * Copyright 2004 The Apache Software Foundation * * Licensed 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 javax.servlet; import java.io.InputStream; import java.net.MalformedURLException; import java.net.URL; import java.util.Enumeration; import java.util.EnumSet; import java.util.EventListener; import java.util.Map; import java.util.Set; import javax.servlet.descriptor.JspConfigDescriptor; /** * Defines a set of methods that a servlet uses to communicate with its * servlet container, for example, to get the MIME type of a file, * dispatch requests, or write to a log file. * * <p>There is one context per "web application" per Java Virtual Machine. (A * "web application" is a collection of servlets and content installed under a * specific subset of the server\'s URL namespace such as <code>/catalog</code> * and possibly installed via a <code>.war</code> file.) * * <p>In the case of a web * application marked "distributed" in its deployment descriptor, there will * be one context instance for each virtual machine. In this situation, the * context cannot be used as a location to share global information (because * the information won\'t be truly global). Use an external resource like * a database instead. * * <p>The <code>ServletContext</code> object is contained within * the {@link ServletConfig} object, which the Web server provides the * servlet when the servlet is initialized. * * @author Various * * @see Servlet#getServletConfig * @see ServletConfig#getServletContext */ public interface ServletContext { /** * The name of the <tt>ServletContext</tt> attribute which stores * the private temporary directory (of type <tt>java.io.File</tt>) * provided by the servlet container for the <tt>ServletContext</tt> */ public static final String TEMPDIR = "javax.servlet.context.tempdir"; /** * The name of the <code>ServletContext</code> attribute whose value * (of type <code>java.util.List<java.lang.String></code>) contains * the list of names of JAR files in <code>WEB-INF/lib</code> ordered by * their web fragment names (with possible exclusions if * <code><absolute-ordering></code> without any * <code><others/></code> is being used), or null if no * absolute or relative ordering has been specified */ public static final String ORDERED_LIBS = "javax.servlet.context.orderedLibs"; /** * Returns the context path of the web application. * * <p>The context path is the portion of the request URI that is used * to select the context of the request. The context path always comes * first in a request URI. If this context is the "root" context * rooted at the base of the Web server\'s URL name space, this path * will be an empty string. Otherwise, if the context is not rooted at * the root of the server\'s name space, the path starts with a / * character but does not end with a / character. * * <p>It is possible that a servlet container may match a context by * more than one context path. In such cases the * {@link javax.servlet.http.HttpServletRequest#getContextPath()} * will return the actual context path used by the request and it may * differ from the path returned by this method. * The context path returned by this method should be considered as the * prime or preferred context path of the application. * * @return The context path of the web application, or "" for the * root context * * @see javax.servlet.http.HttpServletRequest#getContextPath() * * @since Servlet 2.5 */ public String getContextPath(); /** * Returns a <code>ServletContext</code> object that * corresponds to a specified URL on the server. * * <p>This method allows servlets to gain * access to the context for various parts of the server, and as * needed obtain {@link RequestDispatcher} objects from the context. * The given path must be begin with <tt>/</tt>, is interpreted relative * to the server\'s document root and is matched against the context * roots of other web applications hosted on this container. * * <p>In a security conscious environment, the servlet container may * return <code>null</code> for a given URL. * * @param uripath a <code>String</code> specifying the context path of * another web application in the container. * @return the <code>ServletContext</code> object that * corresponds to the named URL, or null if either none exists or the container wishes to restrict * this access. * * @see RequestDispatcher */ public ServletContext getContext(String uripath); /** * Returns the major version of the Servlet API that this * servlet container supports. All implementations that comply * with Version 4.0 must have this method return the integer 4. * * @return 4 */ public int getMajorVersion(); /** * Returns the minor version of the Servlet API that this * servlet container supports. All implementations that comply * with Version 4.0 must have this method return the integer 0. * * @return 0 */ public int getMinorVersion(); /** * Gets the major version of the Servlet specification that the * application represented by this ServletContext is based on. * * <p>The value returned may be different from {@link #getMajorVersion}, * which returns the major version of the Servlet specification * supported by the Servlet container. * * @return the major version of the Servlet specification that the * application represented by this ServletContext is based on * * @throws UnsupportedOperationException if this ServletContext was * passed to the {@link ServletContextListener#contextInitialized} method * of a {@link ServletContextListener} that was neither declared in * <code>web.xml</code> or <code>web-fragment.xml</code>, nor annotated * with {@link javax.servlet.annotation.WebListener} * * @since Servlet 3.0 */ public int getEffectiveMajorVersion(); /** * Gets the minor version of the Servlet specification that the * application represented by this ServletContext is based on. * * <p>The value returned may be different from {@link #getMinorVersion}, * which returns the minor version of the Servlet specification * supported by the Servlet container. * * @return the minor version of the Servlet specification that the * application represented by this ServletContext is based on * * @throws UnsupportedOperationException if this ServletContext was * passed to the {@link ServletContextListener#contextInitialized} method * of a {@link ServletContextListener} that was neither declared in * <code>web.xml</code> or <code>web-fragment.xml</code>, nor annotated * with {@link javax.servlet.annotation.WebListener} * * @since Servlet 3.0 */ public int getEffectiveMinorVersion(); /** * Returns the MIME type of the specified file, or <code>null</code> if * the MIME type is not known. The MIME type is determined * by the configuration of the servlet container, and may be specified * in a web application deployment descriptor. Common MIME * types include <code>text/html</code> and <code>image/gif</code>. * * @param file a <code>String</code> specifying the name of a file * * @return a <code>String</code> specifying the file\'s MIME type */ public String getMimeType(String file); /** * Returns a directory-like listing of all the paths to resources * within the web application whose longest sub-path matches the * supplied path argument. * * <p>Paths indicating subdirectory paths end with a <tt>/</tt>. * * <p>The returned paths are all relative to the root of the web * application, or relative to the <tt>/META-INF/resources</tt> * directory of a JAR file inside the web application\'s * <tt>/WEB-INF/lib</tt> directory, and have a leading <tt>/</tt>. * * <p>The returned set is not backed by the {@code ServletContext} object, * so changes in the returned set are not reflected in the * {@code ServletContext} object, and vice-versa.</p> * * <p>For example, for a web application containing: * * <pre>{@code * /welcome.html * /catalog/index.html * /catalog/products.html * /catalog/offers/books.html * /catalog/offers/music.html * /customer/login.jsp * /WEB-INF/web.xml * /WEB-INF/classes/com.acme.OrderServlet.class * /WEB-INF/lib/catalog.jar!/META-INF/resources/catalog/moreOffers/books.html * }</pre> * * <tt>getResourcePaths("/")</tt> would return * <tt>{"/welcome.html", "/catalog/", "/customer/", "/WEB-INF/"}</tt>, * and <tt>getResourcePaths("/catalog/")</tt> would return * <tt>{"/catalog/index.html", "/catalog/products.html", * "/catalog/offers/", "/catalog/moreOffers/"}</tt>. * * @param path the partial path used to match the resources, * which must start with a <tt>/</tt> * @return a Set containing the directory listing, or null if there * are no resources in the web application whose path * begins with the supplied path. * * @since Servlet 2.3 */ public Set<String> getResourcePaths(String path); /** * Returns a URL to the resource that is mapped to the given path. * * <p>The path must begin with a <tt>/</tt> and is interpreted * as relative to the current context root, * or relative to the <tt>/META-INF/resources</tt> directory * of a JAR file inside the web application\'s <tt>/WEB-INF/lib</tt> * directory. * This method will first search the document root of the * web application for the requested resource, before searching * any of the JAR files inside <tt>/WEB-INF/lib</tt>. * The order in which the JAR files inside <tt>/WEB-INF/lib</tt> * are searched is undefined. * * <p>This method allows the servlet container to make a resource * available to servlets from any source. Resources * can be located on a local or remote * file system, in a database, or in a <code>.war</code> file. * * <p>The servlet container must implement the URL handlers * and <code>URLConnection</code> objects that are necessary * to access the resource. * * <p>This method returns <code>null</code> * if no resource is mapped to the pathname. * * <p>Some containers may allow writing to the URL returned by * this method using the methods of the URL class. * * <p>The resource content is returned directly, so be aware that * requesting a <code>.jsp</code> page returns the JSP source code. * Use a <code>RequestDispatcher</code> instead to include results of * an execution. * * <p>This method has a different purpose than * <code>java.lang.Class.getResource</code>, * which looks up resources based on a class loader. This * method does not use class loaders. * * @param path a <code>String</code> specifying * the path to the resource * * @return the resource located at the named path, * or <code>null</code> if there is no resource at that path * * @exception MalformedURLException if the pathname is not given in * the correct form */ public URL getResource(String path) throws MalformedURLException; /** * Returns the resource located at the named path as * an <code>InputStream</code> object. * * <p>The data in the <code>InputStream</code> can be * of any type or length. The path must be specified according * to the rules given in <code>getResource</code>. * This method returns <code>null</code> if no resource exists at * the specified path. * * <p>Meta-information such as content length and content type * that is available via <code>getResource</code> * method is lost when using this method. * * <p>The servlet container must implement the URL handlers * and <code>URLConnection</code> objects necessary to access * the resource. * * <p>This method is different from * <code>java.lang.Class.getResourceAsStream</code>, * which uses a class loader. This method allows servlet containers * to make a resource available * to a servlet from any location, without using a class loader. * *以上是关于spring-boot-2.0.3源码篇 - filter的注册，值得一看的主要内容，如果未能解决你的问题，请参考以下文章
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