Question

We are using JAX-RS with some fairly basic POJO entities and have a number of @GET and @POST annotated methods that @Produce and @Consume MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML. Nothing spectacular.

Question I have is how best should I validate the data coming in?

We do not have an XML Schema although I could generate one. I would need to hook this in somehow which doesn’t look terribly appealing and I have not found a concise example yet.

We could use “bean validation” but I am again unsure how I might hook this up and invoke it.

Finally (I think) we could for example add some isValidForXXX() methods to the entity POJOs and call them whenever we have an instance handed in to us.

Recommendations anyone?

Answer 1

If you have an XML schema then you could use JAXB validation inside a MessageBodyReader. For a concrete example see my answer to a similar question.

• Validate JAXBElement in JPA/JAX-RS Web Service

ValidatingReader

Below is a bare bones implementation of MessageBodyReader that does four things: 1) Create a JAXBContext, 2) Create an instance of Schema, 3) Sets the schema on the Unmarshaller 4) Unmarshals the InputStream.

package org.example;

import java.io.*;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.net.URL;

import javax.ws.rs.*;
import javax.ws.rs.core.*;
import javax.ws.rs.ext.*;
import javax.xml.XMLConstants;
import javax.xml.bind.*;
import javax.xml.validation.*;

@Provider
@Consumes("application/xml")
public class ValidatingReader implements MessageBodyReader<Customer> {

    @Context
    protected Providers providers;

    private Schema schema;
    private JAXBContext jaxbContext;

    public ValidatingReader() {
        try {
            JAXBContext jc = JAXBContext.newInstance(Customer.class);
            SchemaFactory sf = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
            URL schemaURL = null; // URL for your XML schema
            schema = sf.newSchema(schemaURL);
        } catch(Exception e) {
            throw new RuntimeException(e);
        }
    }

    public boolean isReadable(Class<?> arg0, Type arg1, Annotation[] arg2, MediaType arg3) {
        return arg0 == Customer.class;
    }

    public Customer readFrom(Class<Customer> arg0, Type arg1, Annotation[] arg2, MediaType arg3, MultivaluedMap<String, String> arg4, InputStream arg5)
            throws IOException, WebApplicationException {
        try {
            Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
            unmarshaller.setSchema(schema);
            return (Customer) unmarshaller.unmarshal(arg5);
        } catch(JAXBException e) {
            throw new RuntimeException(e);
        }
    }

}