Java 严重：应用程序 web.xml 中的解析错误
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Severe: Parse error in application web.xml
提问by Dru Freeman
I am trying to teach myself Java, Java EE, and Tomcat pretty much all at once.
(Experienced C/Obj-C dev)
我正在尝试同时自学 Java、Java EE 和 Tomcat。
（有经验的 C/Obj-C 开发者）
I was following a tutorial at YouTube at: http://www.youtube.com/watch?v=bd50C6XUnFw
我正在关注 YouTube 上的教程：http: //www.youtube.com/watch?v=bd50C6XUnFw
I am running:
我在跑步：
- Apache Tomcat/7.0.47
- JVM 1.7.0_45-b18
- Mac OS X 10.8.5 x86_64
- Apache Tomcat/7.0.47
- JVM 1.7.0_45-b18
- Mac OS X 10.8.5 x86_64
The error I'm seeing is:
我看到的错误是：
SEVERE: Parse error in application web.xml file at jndi:/localhost/FirstServlet/WEB-INF/web.xml
org.xml.sax.SAXParseException; systemId: jndi:/localhost/FirstServlet/WEB-INF/web.xml; lineNumber: 8; columnNumber: 19; Error at (8, 19) : Can't convert argument: null
at org.apache.tomcat.util.digester.Digester.createSAXException(Digester.java:2687)
at org.apache.tomcat.util.digester.Digester.createSAXException(Digester.java:2719)
at org.apache.tomcat.util.digester.Digester.endElement(Digester.java:1054)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser.java:609)
As shown in the video the web.xml (at path /Library/Tomcat/webapps/firstservlet/WEB-INF) is:
如视频所示，web.xml（在路径/Library/Tomcat/webapps/firstservlet/WEB-INF）是：
<web-app>
<servlet>
<servlet-name>My FirstServlet</servlet-name>
<servlet-class>FirstServlet</servlet-class>
</servlet>
<servlet-mapping>
<url-pattern>/myfirstservlet</url-pattern>
</servlet-mapping>
</web-app>
The error indicates that the issue is a null it's hitting after the </servlet-mapping>
该错误表明问题是一个空值，它在 </servlet-mapping>
So my only assumption is that the tutorial on YouTube is missing something and I must be missing an argument. Suggestions strongly welcomed.
所以我唯一的假设是 YouTube 上的教程缺少一些东西，我必须缺少一个论点。强烈欢迎提出建议。
采纳答案by PM 77-1
I believe you're missing <servlet-name>...</servlet-name>in <servlet-mapping>section:
我相信你缺少<servlet-name>...</servlet-name>的<servlet-mapping>部分：
<servlet-mapping>
<servlet-name>My FirstServlet</servlet-name>
<url-pattern>/myfirstservlet</url-pattern>
</servlet-mapping>
Have a look at basic web.xml file
回答by Diversity
Between the element servlet-mapping the element servlet-name is missing
在元素 servlet-mapping 之间缺少元素 servlet-name
<servlet-mapping>
<servlet-name>MyFirstServlet</servlet-name>
<url-pattern>/myfirstservlet</url-patter>
</servlet-mapping>
The servlet name is a kind of id which creates a relationship between url and the guven Servlet class.
servlet 名称是一种 id，它在 url 和 guven Servlet 类之间创建关系。
回答by Stephen C
Suggestions strongly welcomed.
强烈欢迎提出建议。
Don't rely on a single tutorial as your sole source of information ...
These things are specified. If you have doubts about the accuracy of a "secondary source" such as a dubious tutorial video, look at the specification.
If reading a specification is too difficult for you1, then look for a reliable tutorial; e.g. for Java-related stuff, look for one written by Oracle.
不要依赖单个教程作为您唯一的信息来源......
这些东西是指定的。如果您对“次要来源”（例如可疑的教程视频）的准确性有疑问，请查看规范。
如果阅读规范对您来说太难1，那么请寻找可靠的教程；例如，对于与 Java 相关的内容，请查找 Oracle 编写的内容。
1 - People who label a specification "obtuse" are probably missing the real point of the specification. A good specification is written with accuracy, precision and completeness as its primary goals. A (so-called) specification that reads like a tutorial is most likely not meeting its primary goals properly.
1 - 给规范贴上“迟钝”标签的人可能忽略了规范的真正要点。一个好的规范是以准确性、精确性和完整性为主要目标的。读起来像教程的（所谓的）规范很可能没有正确实现其主要目标。
In this case, the Servlet spec 3.0(section 14.4.11) makes it clear that you need a servlet-nameelement to say what Servlet the matching requests are mapped to.
在这种情况下，Servlet 规范 3.0（第 14.4.11 节）明确指出您需要一个servlet-name元素来说明匹配请求映射到哪个 Servlet。
(You could most likely find the same information in other tutorials, etcetera ...)
（您很可能会在其他教程等中找到相同的信息......）
