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问题描述

 getServletContext().getRealPath()为临时目录

问题分析

默认情况下Spring Boot中request.getServletContext().getRealPath()返回的是一个临时文件夹的地址

org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory

protected void prepareContext(Host host, ServletContextInitializer[] initializers) {		File documentRoot = getValidDocumentRoot();		TomcatEmbeddedContext context = new TomcatEmbeddedContext();		if (documentRoot != null) {			context.setResources(new LoaderHidingResourceRoot(context));		}		context.setName(getContextPath());		context.setDisplayName(getDisplayName());		context.setPath(getContextPath());		File docBase = (documentRoot != null) ? documentRoot : createTempDir("tomcat-docbase");//关键创建临时文件夹		context.setDocBase(docBase.getAbsolutePath());		context.addLifecycleListener(new FixContextListener());		context.setParentClassLoader((this.resourceLoader != null) ? this.resourceLoader.getClassLoader()				: ClassUtils.getDefaultClassLoader());		resetDefaultLocaleMapping(context);		addLocaleMappings(context);

创建的临时目录位置

org.springframework.boot.web.servlet.server.AbstractServletWebServerFactory

private final DocumentRoot documentRoot = new DocumentRoot(this.logger);    /**	 * Returns the absolute document root when it points to a valid directory, logging a	 * warning and returning {@code null} otherwise.	 * @return the valid document root	 */	protected final File getValidDocumentRoot() {		return this.documentRoot.getValidDirectory();	}

 org.springframework.boot.web.servlet.server.DocumentRoot

/**	 * Returns the absolute document root when it points to a valid directory, logging a	 * warning and returning {@code null} otherwise.	 * @return the valid document root	 */	final File getValidDirectory() {		File file = this.directory;        // If document root not explicitly set see if we are running from a war archive		file = (file != null) ? file : getWarFileDocumentRoot();        // If not a war archive maybe it is an exploded war		file = (file != null) ? file : getExplodedWarFileDocumentRoot();        // Or maybe there is a document root in a well-known location		file = (file != null) ? file : getCommonDocumentRoot();		if (file == null && this.logger.isDebugEnabled()) {			logNoDocumentRoots();		}		else if (this.logger.isDebugEnabled()) {			this.logger.debug("Document root: " + file);		}		return file;	}

发现有三种取路径方式： 

war包 getWarFileDocumentRoot

导出包 getExplodedWarFileDocumentRoot

文档 getCommonDocumentRoot

内置tomcat启动应该属于第三种。

private static final String[] COMMON_DOC_ROOTS = { "src/main/webapp", "public","static" };

private File getCommonDocumentRoot() {		for (String commonDocRoot : COMMON_DOC_ROOTS) {			File root = new File(commonDocRoot);			if (root.exists() && root.isDirectory()) {				return root.getAbsoluteFile();			}		}		return null;	}

百度得知 取的是

System.getProperty("user.dir")

相当于 

File root = new File(System.getProperty("user.dir")+"src/main/webapp")；

输出 System.getProperty("user.dir") 是项目层目录 

解决方案

Spring Boot会尝试读取COMMON_DOC_ROOTS 配置里面的路径

在 Spring Boot 所在的jar包或者项目所在的根目录下新建一个src/main/webapp的目录、public或者static的目录

那么通过 request.getServletContext().getRealPath()就会得到src/main/webapp、public或者static的路径

其中优先级为src/main/webapp>public>static

需要修改到模块目录下

参考：

参考文章

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