Use Groovy has Spring bean in a JSF web application

It’s easy and powerful use Groovy classes in your Java web application using the Spring Framework. Here you can find a tutorial.

In my last project I had to scan a complex xml file and copy the information to a database. A Java class (using org.wc3.dom.* and DocumentBuilder) did the work but the hundreds lines of code were complex and not easy to maintain.

Ex.

DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance(); 
DocumentBuilder        docBuilder        = docBuilderFactory.newDocumentBuilder(); 
doc = docBuilder.parse(fileName); 
doc.getDocumentElement().normalize(); 
NodeList listOfEntries = doc.getElementsByTagName("entry"); 
for (int s = 0; s < listOfEntries.getLength(); s++) { 
  Node firstEntityNode = listOfEntries.item(s); 
  if (firstEntityNode.getNodeType() == Node.ELEMENT_NODE) { 
  ListEntry entry              = new ListEntry(); 
  Element   firstEntityElement = (Element) firstEntityNode; 
  NodeList  uidList            = firstEntityElement.getElementsByTagName("uid"); 
  ... 
[/sourcecode] 
 
For this reason I decided to integrate groovy in the Spring-JSF application, Groovy has the XMLSlurper class that allows to easily access an XML file like if it is a collection of classes. 
 
You can see <a href="https://www.theregister.co.uk/2008/01/11/groovy_xml_part_two/" target="_blank">here</a> a tutorial for SMLSlurper. 
 
In my application the role of the first Groovy class were the following: 
<ul> 
	<li>accept 2 parameters from a traditional java class (xml file address and an integer parameter)</li> 
	<li>process the xml file</li> 
	<li>use 2 existing Java classes</li> 
	<li>return an ArrayList of custom objects with the values found in the list</li> 
</ul> 
<strong>Tasks:</strong> 
 
<strong>1. add the groovy jar to the libraries of your application</strong> 
 
<strong>2. create a traditional Java Interface</strong> 
 
 
package ch.genidea.checknames.importer; 
import java.util.List; 
 
import ch.genidea.checknames.model.ListEntry; 
import ch.genidea.checknames.model.SourceList; 
 
public interface Parser { 
    List parse(); 
    void setFilename(String filename); 
    void setSourceList(SourceList sourceList); 
} 

I had to declare the setters for the 2 variables to import in the groovy class.

3. create the groovy class in the classpath. If you are using maven add it to the src/main/resources directory.

Ex.

package ch.genidea.checknames.importer 
 
import java.util.List; 
import ch.genidea.checknames.model.ListEntry; 
import ch.genidea.checknames.model.SourceList; 
 
public class ParserImpl implements ch.genidea.checknames.importer.Parser{ 
    String filename 
    List <ListEntry> result 
    SourceList sourceList 
 
    public List<ListEntry> parse(){ 
        def pers=new XmlSlurper().parse(new File(filename)) 
 
        List <ListEntry> result = new ArrayList<ListEntry>() 
        def allEntry = pers.Entry 
 
        allEntry.each{ 
                 result.add(addEntry(it)) 
                 it.akaList.aka.each{ 
                 result.add(addEntry(it)) 
                 } 
        } 
        return result 
    } 
    ListEntry addEntry(def it) 
    { 
            ListEntry entity = new ListEntry() 
             entity.uid = (it.uid.text() as Integer) 
             entity.sourceList=sourceList 
             entity.familyName = it.lastName.text() 
             entity.firstName = it.firstName.text() 
             return entity 
    } 
 
    void setFilename(String filename) 
    { 
        this.filename = filename 
    } 
    void setSourceList(SourceList sourceList) 
    { 
        this.sourceList = sourceList 
    } 
 
} 
 

In few lines the class did the same work of hundreds of lines of code of the previous implementation 🙂

In this groovy class we use ListEntry and SourceList that are traditional java classes and we return a List object

4. Declare the bean in Spring

<beans xmlns="https://www.springframework.org/schema/beans" 
xmlns:lang="https://www.springframework.org/schema/lang" 
 ... 
https://www.springframework.org/schema/lang https://www.springframework.org/schema/lang/spring-lang-2.5.xsd" 
... 
> 
<lang:groovy id="parser" script-source="classpath:ch/genidea/checknames/importer/ParserImpl.groovy" /> 
 
<bean name = "listImportService" class="ch.genidea.checknames.lists.service.ListImportServiceImpl"> 
<property name="parser" ref="parser"></property> 
</bean> 
 
 

5. use the groovy class in your sourcecode 🙂

parser.setFilename(fileSource); 
parser.setSourceList(sl); 
List<ListEntry> list = parser.parse(); 

The only drawbacks I had are:

• with Eclipse is not easy to debug groovy, but I used the groovyconsole to test rapidly the changes
• 4MB added using the groovy-all.jar

Small issues compared to the great benefits of having less and more readable codeeasy a