A common format for data exchange between web frontend and backend system is JSON. Most tutorials you find will tell you how to use JAXB (Java API for XML Binding) and its Java annotations for generating JSON. Once you have done what those tutorials told you suddenly you see some very strange JSON fromat which is not what you expected. At this point you might look for other tutorials or blogs that tell you what else you have to do in order to get a natural JSON representation of your POJOs by using JAXB. If you are lucky, then you will find the POJOMappingFeature that is shipped with Jersey. But then you find out that you still have null values in your generated JSON Strings. So you keep asking Google for aome annotations or some other Features like the POJOMappingFeature that allow you to get rid of the null values. Then you find some annotations and code snippets that seem not to work for you because you don’t have the correct libraries or library versions on your Glassfish classpath. With your last breath you have come to a point where you are getting ready to develop your own @Provider classes to generate JSON from POJOs and vice versa. Since you have found this tutorial you don’t have to implement your own @Provider classes and you don’t have to use JAXB.
JAXB is a great thing. But in case you only need JSON and no XML at all, like in our case, then JAXB might not be the best choice. JAXB allows to convert your POJOs to JSON and vice versa. But it always generates XML in an intermediate step and that’s what we actually don’t need. Furthermore you have to annotate your classes with @XmlRootElement, but what happens if you don’t have the sources of classes that you want to convert to JSON? So there can be good reasons for not using JAXB, it depends from case to case… As an alternative you could use Google’s gson (which is by the way really great). But since we are in a Glassfish world (at least here in this tutorial) we will use Jackson (Jersey is based on Jackson). Please keep in mind that I have tested this tutorial with a Glassfish 3.1.2 installation. The 3.1.2 version ships with Jersey 1.11 (you can easily check your Jersey version in the server output when you start your Glassfish, i.e. something like this: Initiating Jersey application, version ‘Jersey: 1.11 12/09/2011 10:27 AM’). By the end of 2011 Jersey was modularized. What we actually want is to have all the jersey-json maven dependencies in our project. But since I have promised not to use Maven you have to add them all one by one to your classpath. Please download all the jars listed on the Jersey Dependencies page under 11.4.1. JAXB (we only need the jersey-json dependencies). Hint: I have added all the relevant dependencies to the /WEB-INF/lib/ folder of the downloadable sources below. If you want some more information about the different Jackson packages please check here. By the way: we are using Jackson 1.9.2 and we want to configure Jackson globally in our own @Provider class. Instead we could also use @Json* annotations, i.e. @JsonSerialize(include = Inclusion.NON_EMPTY). Inclusion.NON_EMPTY tells Jackson not to include null values or empty collections. That’s it – the rest happens without any further configuration Image may be NSFW.
Clik here to view.
Please check here in case you have multiple Providers for the same type.
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
|
package com.nabisoft.jaxrs.provider;import javax.inject.Singleton;import javax.ws.rs.Produces;import javax.ws.rs.core.MediaType;import javax.ws.rs.ext.ContextResolver;import javax.ws.rs.ext.Provider;import org.codehaus.jackson.map.ObjectMapper;import org.codehaus.jackson.map.annotate.JsonSerialize;@Provider@Produces(MediaType.APPLICATION_JSON)@Singletonpublic class MyJacksonJsonProvider implements ContextResolver<ObjectMapper> { private static final ObjectMapper MAPPER = new ObjectMapper(); static { // since Jackson 1.9 // this default configuration can be overwritten via annotations MAPPER.setSerializationInclusion(JsonSerialize.Inclusion.NON_EMPTY); } public MyJacksonJsonProvider() { System.out.println("Constructor called: com.nabisoft.jaxrs.provider.MyJacksonProvider"); } @Override public ObjectMapper getContext(Class<?> type) { System.out.println("MyJacksonProvider.getContext(): "+type); return MAPPER; } }For more details about this check spring web hosting website.
|