How to replace a value in web.xml with a Maven property?

Question

I have a Maven project that downloads some test files into its build directory ./target/files. These files should then be available to a servlet, which I can easily achieve by hardcoding the full path as an <init-param> of the servlet:

<servlet>
    <servlet-name>TestServlet</servlet-name>
    <servlet-class>my.package.TestServlet</servlet-class>
    <init-param>
        <param-name>filepath</param-name>
        <param-value>/home/user/testproject/target/files</param-value>
    </init-param>
</servlet>

How can I avoid hardcoding the full path and use a dynamic parameter replacement instead? I tried the following, but it did not work:

<param-value>${project.build.directory}/files</param-value>

Yuzik

Can you explain in more detail how your project downloads the test files? What triggers that? Normally problems like this are solved by enabling filtering, but it may be difficult depending upon how these files appear. – Hurtful

Answer 1

Add to your pom section:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-war-plugin</artifactId>
    <configuration>
        <webResources>
            <resource>
                <filtering>true</filtering>
                <directory>src/main/webapp</directory>
                <includes>
                    <include>**/web.xml</include>
                </includes>
            </resource>
        </webResources>
    </configuration>
</plugin>

See Maven: Customize web.xml of web-app project for more details

Kaddish

See also maven.apache.org/plugins/maven-war-plugin/examples/… for more info – Balder

What's in the solution that enables the replacement? – Lowis

@alikelzin-kilaka: you can define a property in your pom.xml (e.g. "<myProp>Moin</myProp>") and if you have in your web.xml a placeholder ("${myProp}") this will be replaced with the value of your property (with "Moin" in my sample) – Parasitize

This one is actually replacing the placeholder with actual value from the pom property, but after deploying its giving error saying -- java.lang.IllegalArgumentException: Could not resolve placeholder 'spring.profiles.to.active' in string value "${spring.profiles.to.active}". Whereas in .war and inside target folder its the new value. Any idea why its happening so? – Godric

@JohnMaclein I am having the same issue. It seems that all the found files are copied to the "warSourceDirectory". That means that the web.xml will be placed into the root folder. However: The <webXml> tag is reading from the original WEB-INF folder where the property isn't replaced. Try "<webXml>src/main/webapp/web.xml</webXml>" – Grallatorial

I believe that <filtering>true</filtering> is what does the trick of variable replacement – Floorer

copy/paste, this solution worked perfectly. Now I was able to make a context param dependent on ${environment} – Orthorhombic

@Grallatorial actually you should not specify the <webXml> tag at all to make it work with m2e-wtp (deploying to servers from Eclipse). see issues.redhat.com/browse/JBIDE-16341 and bugs.eclipse.org/bugs/show_bug.cgi?id=487370#c13 – Gallup

Answer 2

You can simply use maven filtering resources:

<build>
    ...
    <resources>
      <resource>
        <directory>src/main/resources</directory>
        <filtering>true</filtering>
      </resource>
      ...
    </resources>
    ...
  </build>
  ...
</project>

You can also combine this and would like to filter some files whereas others shouldn't be filtered:

   <resources>
      <resource>
        <directory>src/main/resources</directory>
        <filtering>true</filtering>
        <includes>
          <include>**/*.xml</include>
        </includes>
      </resource>
      <resource>
        <directory>src/main/resources</directory>
        <filtering>false</filtering>
        <excludes>
          <exclude>**/*.xml</exclude>
        </excludes>
      </resource>
      ...
    </resources>

Put appropriate placeholders into the files you would like having replaced things like ${home}.

Coulombe

This code does filters and replace strings in XML files with the values defined in the pom.xml <properties> tag or do I need to use a properties file? – Cubiform

Answer 3

You can use Replace Ant Task to do it.

Heres a sample Implementation where i replace the tokenkeys in a property file , adapt it to suit your needs

test.properties

SERVER_NAME=@SERVER_NAME@
PROFILE_NAME=@PROFILE_NAME@

pom.xml

 <plugin>
    <artifactId>maven-antrun-plugin</artifactId>
    <version>1.7</version>
    <executions>
      <execution>
        <phase>compile</phase>
        <configuration>
          <tasks>

            <replace dir="${basedir}/src/main/resources" >
              <include name="**/*.properties"/>
             <replacefilter     token="@SERVER_NAME@" value="My Server"/>
             <replacefilter     token="@PROFILE_NAME@" value="My Profile"/>
            </replace>             

          </tasks>
        </configuration>
        <goals>
          <goal>run</goal>
        </goals>
      </execution>
    </executions>
  </plugin> 

voila! Now execute

mvn clean package

Observatory

Better use resources filtering instead of Ant. – Coulombe

While the accepted answer is better for the actual question asked, this is actually exactly what I was looking for so I could replace versions for webjar dependencies in static html files. Thanks! – Mingmingche

Answer 4

I think you can use maven-war-plugin's filteringDeploymentDescriptors option to filter deployment descriptors -

<properties>
    <maven.war.filteringDeploymentDescriptors>true</maven.war.filteringDeploymentDescriptors>
</properties>

Geminate

Answer 5

Add maven-war-plugin and set <filteringDeploymentDescriptors>true</filteringDeploymentDescriptors> to replace the placeholder when running mvn package

<properties>
  <project.build.directory>your path</project.build.directory>
</properties>

<build>
  <plugin>
    <artifactId>maven-war-plugin</artifactId>
    <version>3.2.2</version>
    <configuration>
      <filteringDeploymentDescriptors>true</filteringDeploymentDescriptors>
    </configuration>
  </plugin>
</build>

Tini

Answer 6

Coding maven parameters in web.xml can't work directly, because at run time, when your application starts, maven has finished its work and the application has no knowledge about maven.

You can filter an alternative web.xml (see maven filtering: http://maven.apache.org/plugins/maven-resources-plugin/examples/filter.html) and use it when building the war (see the webXml parameter at the war plugin documentation: http://maven.apache.org/plugins/maven-war-plugin/war-mojo.html)

Alon