Groovy: copy XML elements from one doc to another

Question

I am new to Groovy and am stuck with a simple problem. All I wanna do is extract certain elements from one XML file and created a new file with it. Here's an example XML, let's use a Maven pom file:

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.group</groupId>
  <artifactId>artifact</artifactId>
  <version>1.4</version>
  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.8.2</version>
        <scope>test</scope>
      </dependency>
    </dependencies>
 </dependencyManagement>

I know how to parse XML in Groovy:

def project = new XmlParser().parse("pom.xml")
project.groupId.each{
  println it.text()
}

I also know how to create XML in Groovy:

def xml = new groovy.xml.MarkupBuilder()
xml.project (){
  modelVersion("artifactId")
  groupId("com.group")
  artifactId("artifact")
}

However, I seem to have a problem combining the two. I want, for example, take groupId, artifactId and the whole dependencies tree and create a new XML from it. It can't be that hard and I wanna make use of the Groovy simplicity.

Something along those lines (of course this does not work):

def newXml= new groovy.xml.MarkupBuilder()
newXml.groupId= project.groupId
newXml.dependencies = project.dependencyManagement.dependencies

---

Thanks. That code helped a lot but how can I handle the namespace, i.e. if the project tag in the input looks like that:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

It is then adding some weird annotations to the output. All I want is that the project tag in the output looks like that as well.

Answer 1

You can do this with XmlSlurper:

import groovy.xml.*

def pxml = '''<project>
             |  <modelVersion>4.0.0</modelVersion>
             |  <groupId>com.group</groupId>
             |  <artifactId>artifact</artifactId>
             |  <version>1.4</version>
             |  <dependencyManagement>
             |    <dependencies>
             |      <dependency>
             |        <groupId>junit</groupId>
             |        <artifactId>junit</artifactId>
             |        <version>4.8.2</version>
             |        <scope>test</scope>
             |      </dependency>
             |    </dependencies>
             |  </dependencyManagement>
             |</project>'''.stripMargin()

def p = new XmlSlurper().parseText( pxml )

String nxml = new StreamingMarkupBuilder().bind {
  project {
    dependecyManagement {
      dependencies {
        mkp.yield p.dependencyManagement.dependencies.children()
      }
    }
  }
}

println XmlUtil.serialize( nxml )

Which prints:

<?xml version="1.0" encoding="UTF-8"?>
<project>
  <dependecyManagement>
    <dependencies>
      <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.8.2</version>
        <scope>test</scope>
      </dependency>
    </dependencies>
  </dependecyManagement>
</project>

To handle the namespaces better, you could try:

def pxml = '''<project xmlns="http://maven.apache.org/POM/4.0.0"
             |         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             |         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
             |  <modelVersion>4.0.0</modelVersion>
             |  <groupId>com.group</groupId>
             |  <artifactId>artifact</artifactId>
             |  <version>1.4</version>
             |  <dependencyManagement>
             |    <dependencies>
             |      <dependency>
             |        <groupId>junit</groupId>
             |        <artifactId>junit</artifactId>
             |        <version>4.8.2</version>
             |        <scope>test</scope>
             |      </dependency>
             |    </dependencies>
             |  </dependencyManagement>
             |</project>'''.stripMargin()

def p = new XmlSlurper().parseText( pxml )

String nxml = new StreamingMarkupBuilder().bind {
  mkp.declareNamespace(    '':"http://maven.apache.org/POM/4.0.0",
                        'xsi':"http://www.w3.org/2001/XMLSchema-instance" )
  project( 'xsi:schemaLocation':p.@schemaLocation ) {
    dependecyManagement {
      dependencies {
        mkp.yield p.dependencyManagement.dependencies.children()
      }
    }
  }
}

println XmlUtil.serialize( nxml )

Which should give you:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <dependecyManagement>
    <dependencies>
      <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.8.2</version>
        <scope>test</scope>
      </dependency>
    </dependencies>
  </dependecyManagement>
</project>