将参数传递到REST Web服务

Question

I'm dealing with the problem with passing parameteres to web-service.

I have created web-service which works OK for the case fromLanguage = "eng"

But, when I test service through Glassfish console and send fromLanguage = "bos" I don't get appropriate result.

package pckgTranslator;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;

@Path("/MyRestService/{wordToTranslate},{fromLanguage},{toLanguage}")
public class clsTranslate {
@GET
public String doGet(@PathParam("wordToTranslate") String wordToTranslate, 
        @PathParam("fromLanguage") String fromLanguage, @PathParam("toLanguage")  String toLanguage) 
        throws Exception{
    Translator translator = new Translator();
    return translator.getTranslation(wordToTranslate,fromLanguage, toLanguage);        
}

}

This is XML fajl which I try to parse:

<?xml version="1.0" encoding="utf-8" ?>
<gloss>
    <word id="001">
        <eng>ball</eng>
        <bos>lopta</bos>
    </word>
    <word id="002">
        <eng>house</eng>
        <bos>kuca</bos>
    </word>
    <word id="003">
        <eng>game</eng>
        <bos>igra</bos>
    </word>
</gloss>

And this is the class which I'm using for parsing XML.

package pckgTranslator;
import java.io.IOException;
import java.io.InputStream;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

public class Translator {

String translation = null;

String getTranslation(String wordForTransl, String fromLanguage, String toLanguage)
        throws ParserConfigurationException, SAXException, IOException, XPathExpressionException {

    //fromLanguage = "eng";
    //toLanguage = "bos";

    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setNamespaceAware(true);

    DocumentBuilder builder = factory.newDocumentBuilder();
    InputStream is = Translator.class.getResourceAsStream("/resource/glossary.xml");
    Document doc = builder.parse(new InputSource(is));

    XPathFactory xpathfactory = XPathFactory.newInstance();
    XPath xpath = xpathfactory.newXPath();

    //XPathExpression expr = null; //xpath.compile("//word[eng='house']/bos/text()");
    XPathExpression expr = xpath.compile("//word['" + wordForTransl + "'='" + wordForTransl + "']/bos/text()");
    if (fromLanguage == "eng") {
        expr = xpath.compile("//word[eng='" + wordForTransl + "']/bos/text()");
    } else if (fromLanguage == "bos") {
        expr = xpath.compile("//word[bos='" + wordForTransl + "']/eng/text()");

    }

    Object result = expr.evaluate(doc, XPathConstants.NODESET);
    NodeList nodes = (NodeList) result;
    for (int i = 0; i < nodes.getLength(); i++) {
        //System.out.println(nodes.item(i).getNodeValue());
        translation = nodes.item(i).getNodeValue();
    }
    //return nodes.item(i).getNodeValue();
    if (translation != null) {
        return translation;
    } else {
        return "We are sorry, there is no translation for this word!";
        }
    }
}

It seems to me that something is wrong with the parameters fromLanguage and toLanguage, but I can't realize what exactly. Thanks in advance.

Answer 1

As I mentioned in the comment, you have hardcoded fromLanguage and toLanguage variables to eng and bos at the beginning of getTranslation() method. Due to this, the fromLanguage and 'toLangugae values passed to getTranslation()` method are lost.

Secondly, instead of separating @PathParm by , separate those by / . It will look like:

@Path("/MyRestService/{wordToTranslate}/{fromLanguage}/{toLanguage}")
@GET
public String doGet(@PathParam("wordToTranslate") String wordToTranslate, 
@PathParam("fromLanguage") String fromLanguage, @PathParam("toLanguage")  String toLanguage) throws Exception

Invocation: curl -X GET http://localhost:8080/MyRestService/x/y/z

Alternatively use @QueryParam . In that case your path would be:

@Path("/MyRestService")
public String doGet(@QueryParam("wordToTranslate") String wordToTranslate, 
@QueryParam("fromLanguage") String fromLanguage, @QueryParam("toLanguage")  String toLanguage) throws Exception

Invocation: curl -X GET http://localhost:8080/MyRestService?wordToTranslate=x&fromLanguage=y&toLanguage=z

Remove or comment the below lines in getTranslation() method:

fromLanguage = "eng";
toLanguage = "bos";

---

Note: To fix your issue the above solution is sufficient . However, to make you code better please see the below suggestions. In addition to the above I see two more issues:

• You are storing translated value in translation instance variable. In case you are using the same Translator object (singleton instance) and the current translation fails, getTranslation() will return the previously translated value.
• Why are you initializing expr with the below?

   XPathExpression expr = xpath.compile("//word['" + wordForTransl + "'='" + wordForTransl + "']/bos/text()");

• Lastly, every time you are calling getTranslation() the XML is being parsed. Instead, parse it once in init() method and then use it in getTranslation() method.

I have modified your Translator class based on the above points:

package org.openapex.samples.misc.parse.xml;

import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.*;
import java.io.IOException;
import java.io.InputStream;

public class ParseXMLAndTranslate {
    public static void main(String[] args) throws Exception{
        Translator translator = new Translator();
        translator.init();
        System.out.println(translator.getTranslation("house","eng", "bos"));
        System.out.println(translator.getTranslation("igra","bos", "eng"));
    }

    private static class Translator {
        //String translation = null;
        private Document doc;
        public void init() throws ParserConfigurationException, SAXException, IOException{
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            factory.setNamespaceAware(true);
            DocumentBuilder builder = factory.newDocumentBuilder();
            InputStream is = Translator.class.getResourceAsStream("/resource/glossary.xml");
            this.doc = builder.parse(new InputSource(is));
        }

        String getTranslation(String wordForTransl, String fromLanguage, String toLanguage)
                throws XPathExpressionException {
            //fromLanguage = "eng";
            //toLanguage = "bos";
            XPathFactory xpathfactory = XPathFactory.newInstance();
            XPath xpath = xpathfactory.newXPath();

            //XPathExpression expr = null; //xpath.compile("//word[eng='house']/bos/text()");
            //XPathExpression expr = xpath.compile("//word['" + wordForTransl + "'='" + wordForTransl + "']/bos/text()");
            XPathExpression expr = null;
            if (fromLanguage == "eng") {
                expr = xpath.compile("//word[eng='" + wordForTransl + "']/bos/text()");
            } else if (fromLanguage == "bos") {
                expr = xpath.compile("//word[bos='" + wordForTransl + "']/eng/text()");
            }

            Object result = expr.evaluate(doc, XPathConstants.NODESET);
            NodeList nodes = (NodeList) result;
            String translation = null;
            /*for (int i = 0; i < nodes.getLength(); i++) {
                //System.out.println(nodes.item(i).getNodeValue());
                translation = nodes.item(i).getNodeValue();
            }*/
            if(nodes.getLength() > 0){
                translation = nodes.item(0).getNodeValue();
            }
            //return nodes.item(i).getNodeValue();
            if (translation != null) {
                return translation;
            } else {
                return "We are sorry, there is no translation for this word!";
            }
        }
    }
}

Here is the output:

kuca
game