Java Servlets – Storing a list of values in web.xml (multiple param-value’s for single param-name)

javaservletsweb-applicationsweb.xml

I'm creating a servlet that needs to load configuration information. Part of the configuration information I need is a list of Strings (specifically, a list of hostnames and/or URLs).

I was hoping to store this information in my servlet's web.xml file (so I don't have to write my own parser) as either a context-param or init-param; essentially multiple param-value's for a single param-name.

Example of what I would like:

<context-param>
    <param-name>validHosts</param-name>
    <param-value>example1.com</param-value>
    <param-value>example2.com</param-value>
    <param-value>example3.com</param-value>
</context-param>

My initial research seems to indicate this is not possible–that there can only be a single param-value for any param-name (within either context-param or init-param).

I know I could just use a delimited list within a single param-value, but is that really my only option if I still want to use web.xml? Should I just stop whining and write my own config file parser?

Best Answer

Servlet spec says that you can have only one value for any context parameter. So, you are left with going with delimited list only.

<context-param>
  <param-name>validHosts</param-name>
  <param-value>example1.com,example2.com,.....</param-value>
</context-param>

Related Solutions

Java – How to register multiple servlets in web.xml in one Spring application

As explained in this thread on the cxf-user mailing list, rather than having the CXFServlet load its own spring context from user-webservice-servlet.xml, you can just load the whole lot into the root context. Rename your existing user-webservice-servlet.xml to some other name (e.g. user-webservice-beans.xml) then change your contextConfigLocation parameter to something like:

<servlet>
  <servlet-name>myservlet</servlet-name>
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  <load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
  <servlet-name>myservlet</servlet-name>
  <url-pattern>*.htm</url-pattern>
</servlet-mapping>

<context-param>
  <param-name>contextConfigLocation</param-name>
  <param-value>
    /WEB-INF/applicationContext.xml
    /WEB-INF/user-webservice-beans.xml
  </param-value>
</context-param>

<servlet>
  <servlet-name>user-webservice</servlet-name>
  <servlet-class>org.apache.cxf.transport.servlet.CXFServlet</servlet-class>
  <load-on-startup>2</load-on-startup>
</servlet>

<servlet-mapping>
  <servlet-name>user-webservice</servlet-name>
  <url-pattern>/UserService/*</url-pattern>
</servlet-mapping>

Java – Adding multiple servlets in single web.xml

This isn't going to work. The one which is mapped on /* overtakes all requests. You need to map it on / instead so that it will only intercept on requests which are not matched by all other existing servlets (including the JSP servlet which is implicitly mapped on *.jsp and all "normal" static resources like CSS/JS/image files!). See also Difference between / and /* in servlet mapping url pattern.

If being able to serve static resources is also required, then better map it on a more specific URL pattern like /ws/* and create a Filter which checks the request URI and then forwards accordingly. That filter can in turn safely be mapped on /*. See also this answer for a more concrete code example: How to access static resources when mapping a global front controller servlet on /*.

Best Answer

Related Solutions

Java – How to register multiple servlets in web.xml in one Spring application

Java – Adding multiple servlets in single web.xml

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