java - How to Convert a Properties Object to JSON Object with JAXB

Question

I want to accept and respond JSON objects in a REST Application. The data I need to send and receive are in a .properties file. I have already read them and are now in a Properties Object(From java.util.Properties). Is there a way to marshal and unmarshal Properties Objects, without implementing a new class?

I am using Jax-rs API in a Weblogic server.

@POST
@Path("{id}")
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
public JSONObject getbyID(@PathParam("id")JSONObject inputJsonObj) {
    //marshalling and unmarshalling goes here
}

Answer 1

Not too familiar with WebLogic, so I don't know what version of Jersey it used (1.x or 2.x), but with the 1.x you can simply add this dependency

<dependency>
    <groupId>com.sun.jersey</groupId>
    <artifactId>jersey-json</artifactId>
    <version>${jersey-version}</version>
</dependency>

which will depend on Jackson. Jackson already deserializes and serializes the Properties object to a JSON object.

Here's a simple test

Resource

@Path("/properties")
public class PropertiesResource {

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public Response getProperties() throws Exception {
        FileInputStream fis = new FileInputStream("test.properties");
        Properties props = new Properties();
        props.load(fis);
        return Response.ok(props).build();
    }

    @POST
    @Consumes(MediaType.APPLICATION_JSON)
    public Response postProperties(Properties properties) {
        StringBuilder builder = new StringBuilder();
        for (String key: properties.stringPropertyNames()) {
            builder.append(key).append("=")
                    .append(properties.getProperty(key)).append("
");
        }
        return Response.created(null).entity(builder.toString()).build();
    }
}

Test

public void testMyResource() throws Exception {
    ClientConfig config = new DefaultClientConfig();
    config.getClasses().add(JacksonJsonProvider.class);
    config.getFeatures().put(JSONConfiguration.FEATURE_POJO_MAPPING, 
                                                       Boolean.TRUE);

    Client c = Client.create(config);

    WebResource resource = c.resource(Main.BASE_URI).path("properties");
    String json = resource.accept("application/json").get(String.class);
    System.out.println(json);

    FileInputStream fis = new FileInputStream("test.properties");
    Properties props = new Properties();
    props.load(fis);
    String postResponse 
            = resource.type("application/json").post(String.class, props);
    System.out.println(postResponse);
}

Results:

// from get
{"prop3":"value3","prop2":"value2","prop1":"value1"}

// from post
prop3=value3
prop2=value2
prop1=value1

For the configuration, you just need to configure the POJOMapping Feature and register the Jackson provider

Programmatic

public class JerseyApplication extends ResourceConfig {
    public JerseyApplication() {
        packages(...);
        getProviderClasses().add(JacksonJsonProvider.class);
        getFeatures().put(JSONConfiguration.FEATURE_POJO_MAPPING, Boolean.TRUE);
    }
}

web.xml

<init-param>
    <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
    <param-value>true</param-value>
</init-param>

---

With Jersey 2.x, it's a little bit simpler. We just need this provider

<dependency>
    <groupId>com.fasterxml.jackson.jaxrs</groupId>
    <artifactId>jackson-jaxrs-json-provider</artifactId>
    <version>2.4.0</version>
</dependency>

And register the same JacksonJaxbJsonProvider (though different package, the class name is the same). No Pojo Mapping Feature needed.

---

Note: In both cases, there are two Jackson providers, a JacksonJsonProvider and a JacksonJaxbJsonProvider. If you want the marshalling of pojos to depend on JAXB annotations, then you should register the latter.