Tomcat 7 到 8.5 升级:getResourceAsStream 抛出 NPE [英] Tomcat 7 to 8.5 upgrade : getResourceAsStream throws NPE

问题描述

我是这项 Dev Ops 工作的新手，所以请原谅我可能忽略的任何简单内容.我正在从 Tomcat 7 升级到 8.5.除了 apache 网站和使用 7 到 8 然后是 8 到 8.5.一切似乎没问题，期待当我启动应用程序并且代码尝试使用以下内容加载信息

I am new to this Dev Ops work so please forgive anything simple which I may have overlooked. I am in the middle of upgrading from Tomcat 7 to 8.5. There is not much in terms of migration manuals other then the apache website and using the 7 to 8 then the 8 to 8.5. All seems ok, expect for when I start up the application and the code tries to load information using the following

Thread.currentThread().getContextClassLoader().getResourceAsStream("sql/");

或

getClass().getClassLoader().getResourceAsStream("sql/");

上下文路径正在使用 ROOT.xml 加载，它有一个 docBase 指向位于 ../tomcat/databaseLink 目录中的项目.WEB-INF/classes 文件夹在 ../tomcat/databaseLink 目录下，sql 文件夹在 WEB-INF/classes 文件夹.所以看起来一切正常.

The context path is being loaded using ROOT.xml which has a docBase pointing at the project which is in the ../tomcat/databaseLink directory. The WEB-INF/classes folder is in the ../tomcat/databaseLink directory and the sql folder is in the WEB-INF/classes folder. So it all seems to be ok.

当代码运行时，它看起来像是在 ../tomcat/lib/ 目录中寻找 sql 文件夹而不是 ../tomcat/databaseLink/WEB-INF/classes/sql/ 目录.我没有对默认的 Tomcat 8 conf 文件进行任何更改.知道为什么会发生这种情况或我错过了什么吗?

When the code is running it looks like it is looking for the sql folder in the ../tomcat/lib/ directory rather then the ../tomcat/databaseLink/WEB-INF/classes/sql/ directory. I have not made any changes to the default Tomcat 8 conf files. Any idea why this is happening or what I have missed?

推荐答案

ClassLoader#getResourceAsStream 只查找资源，这些资源位于 Web 应用程序类路径上，即:

The method ClassLoader#getResourceAsStream only finds resources, which are on the web application classpath, i.e.:

• 在文件夹 WEB-INF/classes 或 WEB-INF/lib 文件夹内的 JAR 文件中，
• 在 Tomcat 的 Shared、Common、System 或 Bootstrap 类加载器的类路径中(参见 Tomcat 文档).如您所见，默认情况下，Common 类加载器在其类路径中包含目录 $CATALINA_HOME/lib 和 $CATALINA_BASE/lib.

• in the folder WEB-INF/classes or in a JAR file inside the WEB-INF/lib folder,
• in the classpath of Tomcat's Shared, Common, System or Bootstrap classloaders (cf. Tomcat documentation). As you noticed, by default the Common classloader has the directories $CATALINA_HOME/lib and $CATALINA_BASE/lib in its classpath.

您正在寻找的方法是 ServletContext#getResourceAsStream，在应用目录和WEB中所有JAR的META-INF/resources条目中搜索-INF/lib.所以你应该打电话:

The method you are looking for is ServletContext#getResourceAsStream, which searches in the application directory and META-INF/resources entries of all JARs in WEB-INF/lib. So you should call:

servletContext.getResourceAsStream("/WEB-INF/sql/your_file");

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