XPath issue in Maven replacer plugin -

i following error when trying use xpath replace in web.xml maven replacer plugin

[error] failed execute goal com.google.code.maven-replacer-plugin:replacer:1.5.2:replace (default) on project my-project:  error during xml replacement: content not allowed in prolog. -> [help 1] 

and here's maven code

<plugin>     <groupid>com.google.code.maven-replacer-plugin</groupid>     <artifactid>replacer</artifactid>      <version>1.5.2</version>      <executions>         <execution>             <phase>prepare-package</phase> <goals>                 <goal>replace</goal>              </goals>          </execution>      </executions>      <configuration>         <file>src/main/webapp/web-inf/web.xml</file>         <outputfile>target/web.xml</outputfile>          <regexflags>             <regexflag>case_insensitive</regexflag>          </regexflags>  <replacements>      <replacement>         <xpath>/web-app/display-name</xpath>         <token>.*</token>          <value>${project.name}</value>      </replacement>  </replacements> </plugin> 

web.xml

<?xml version="1.0" encoding="utf-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/xmlschema-instance"      xmlns="http://java.sun.com/xml/ns/javaee"      xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"      xsi:schemalocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"      id="my-project"      version="2.5">      <display-name>my project</display-name>     ... </web-app> 

any idea why?

you need register "http://java.sun.com/xml/ns/javaee" namespace, , choose prefix, let's "javaee", , use /javaee:web-app/javaee:display-name xpath expression.

according link, can in plugin's <configuration> section:

<plugin>     ...      <configuration>         <namespacecontexts>             <javaee>http://java.sun.com/xml/ns/javaee</javaee>         </namespac‌​econtexts>         ...