Question

I’m trying to parse an XML using Groovy and the ScriptEngine API of Java.
The code below does exactly that but I wanted to know if there are any better ways of doing the same. And also if there are any performance implications related to this?

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
/*
<books>
    <book id="1">
        <name>"Catcher In the Rye"</name>
        <author>J.D. Salinger</author>
    </book>
    <book id="2">
      <name>"KiteRunner"</name>
      <author>Khaled Hosseini</author>
    </book>
</books>
*/

public class XMLParsing{
  public static void main(String[] args) {
    Map<String, ArrayList<String>> resultMap 
                                     = new HashMap<String, ArrayList<String>>();
    resultMap = getBookDetails("c:\\temp\\book.xml");
    System.out.println(resultMap);
  }


  public static Map<String ArrayList<String>> getBookDetails(String scriptXml) {
    Map<String, ArrayList<String>> resultMap = 
                                       new HashMap<String, ArrayList<String>>();
    ScriptEngineManager factory = new ScriptEngineManager();
    ScriptEngine engine = factory.getEngineByName("groovy");
    String fact = "import java.util.HashMap;" 
                + "import java.util.ArrayList;" 
                + "def getBookInformation(n){" 
                + "def map1 = new HashMap();" 
                + "xmlDesc = new XmlSlurper().parse(n);" 
                + "xmlDesc.book.findAll{it}.each {"
                + "def list1 = new ArrayList();" 
                + "def id = it.@id;" 
                +
                //"println id;"+
                  "def name = it.name;" 
                + "def author = it.author;" 
                + "list1.add(name);" 
                +  "list1.add(author);" 
                + "map1.put(id, list1);" 
                + "};" 
                + "return map1;}";
    try {
      engine.eval(fact);
      Invocable inv = (Invocable) engine;
      Object[] params = {scriptXml};          
      resultMap = (Map<String,ArrayList<String>>)  
                  inv.invokeFunction("getBookInformation", params);
    } catch (ScriptException e) {
      e.printStackTrace();
    } catch (NoSuchMethodException e) {
      e.printStackTrace();
    }
    return resultMap;
  }
}

Output:

{1=["Catcher In the Rye", J.D. Salinger], 2=["KiteRunner", Khaled Hosseini]}

Answer 1

Your Groovy script could be “groovy-er”…

This does the same thing:

  String fact = "def getBookInformation(n) {" +
                "  xmlDesc = new XmlSlurper().parse(n)\n" +
                "  xmlDesc.book.findAll().collectEntries {\n"+
                "    [ (it.@id):[ it.name, it.author ] ]\n" +
                "  }\n" +
                "}" ; 

Indeed, you could use the GroovyShell rather than the JVM scripting engine, and that gets you down to:

import java.util.ArrayList;
import java.util.Map;
import groovy.lang.Binding ;
import groovy.lang.GroovyShell ;

public class XMLParsing {
  public static void main(String[] args) {
    Map<String, ArrayList<String>> resultMap = getBookDetails("test.xml");
    System.out.println(resultMap);
  }

  public static Map<String, ArrayList<String>> getBookDetails( String scriptXml ) {
    Binding b = new Binding() ;
    b.setVariable( "xmlFile", scriptXml ) ;
    GroovyShell shell = new GroovyShell( b ) ;
    Object ret = shell.evaluate( "new XmlSlurper().parse( xmlFile ).book.findAll().collectEntries { [ (it.@id):[ it.name, it.author ] ] }" ) ;
    return (Map<String, ArrayList<String>>)ret ;
  }
}