Restful , javaEE & json

WebComponent over JAVA EE

Lets think about JSON


JSON is a text-based data exchange format derived from JavaScript that is used in web services and other connected applications. The following sections provide an introduction to JSON syntax, an overview of JSON uses, and a description of the most common approaches to generate and parse JSON.

JSON Syntax

JSON defines only two data structures: objects and arrays. An object is a set of name-value pairs, and an array is a list of values. JSON defines six data types: string, number, object, array, true, false and null.

The following example shows JSON data for a sample object that contains name-value pairs. The value for the name "phoneNumbers" is an array whose elements are two objects.

{
   "firstName": "Duke",
   "lastName": "Java",
   "age": 18,
   "streetAddress": "100 Internet Dr",
   "city": "JavaTown",
   "state": "JA",
   "postalCode": "12345",
   "phoneNumbers": [
      { "Mobile": "111-111-1111" },
      { "Home": "222-222-2222" }
   ]
}

Class or Interface:

   Main Classes and Interfaces in javax.json

Class or Interface	Description
Json	Contains static methods to create instances of JSON parsers, builders, generators. This class also contains methods to create parser, builder, and generator factory objects.
JsonReader	Reads JSON data from a stream and creates an object model in memory.
JsonObjectBuilder JsonArrayBuilder	Create an object model or an array model in memory by adding elements from application code.
JsonWriter	Writes an object model from memory to a stream.
JsonValue	Represents an element (such as an object, an array, or a value) in JSON data.
JsonStructure	Represents an object or an array in JSON data. This interface is a subtype of JsonValue.
JsonObject JsonArray	Represent an object or an array in JSON data. These two interfaces are subtypes of JsonStructure.
JsonString JsonNumber	Represent data types for elements in JSON data. These two interfaces are subtypes of JsonValue.
JsonException	Indicates that a problem occurred during JSON processing.

Classes and Interfaces in javax.json.stream

Class or Interface	Description
JsonParser	Represents an event-based parser that can read JSON data from a stream or from an object model.
JsonGenerator	Writes JSON data to a stream one element at a time.

Example:

import javax.json.Json;
import javax.json.JsonObject;
...
JsonObject model = Json.createObjectBuilder()
   .add("firstName", "Duke")
   .add("lastName", "Java")
   .add("age", 18)
   .add("streetAddress", "100 Internet Dr")
   .add("city", "JavaTown")
   .add("state", "JA")
   .add("postalCode", "12345")
   .add("phoneNumbers", Json.createArrayBuilder()
      .add(Json.createObjectBuilder()
         .add("type", "mobile")
         .add("number", "111-111-1111"))
      .add(Json.createObjectBuilder()
         .add("type", "home")
         .add("number", "222-222-2222")))
   .build();

Functions of JsonObject 

JsonObjectBuilder add(String name, BigDecimal value)
JsonObjectBuilder add(String name, BigInteger value)
JsonObjectBuilder add(String name, boolean value)
JsonObjectBuilder add(String name, double value)
JsonObjectBuilder add(String name, int value)
JsonObjectBuilder add(String name, JsonArrayBuilder builder)
JsonObjectBuilder add(String name, JsonObjectBuilder builder)
JsonObjectBuilder add(String name, JsonValue value)
JsonObjectBuilder add(String name, long value)
JsonObjectBuilder add(String name, String value)
JsonObjectBuilder addNull(String name)

FileWriter writer = new FileWriter("test.txt");
JsonGenerator gen = Json.createGenerator(writer);
gen.writeStartObject()
   .write("firstName", "Duke")

JSON in Java EE RESTful Web Services




What Are RESTful Web Services?


JavaEE tutorial said that "Representational State Transfer (REST) is an architectural style of client-server application centered around the transfer of representations of resources through requests and responses"




We have to have in mind the following concepts:




Uniform interface

URI

HTTP METHODS  POST,GET,DELETE,PUT  

Self-descriptive messages HTML,XHTML,JSON,XML,Images

Stateful interactions through links

Summary of JAX-RS Annotations (by javaEE tutorial)

Annotation
Description

@Path
The @Path annotation's value is a relative URI path indicating where the Java class will be hosted: for example, /helloworld. You can also embed variables in the URIs to make a URI path template. For example, you could ask for the name of a user and pass it to the application as a variable in the URI: /helloworld/{username}.
@GET
The @GET annotation is a request method designator and corresponds to the similarly named HTTP method. The Java method annotated with this request method designator will process HTTP GET requests. The behavior of a resource is determined by the HTTP method to which the resource is responding.
@POST
The @POST annotation is a request method designator and corresponds to the similarly named HTTP method. The Java method annotated with this request method designator will process HTTP POST requests. The behavior of a resource is determined by the HTTP method to which the resource is responding.
@PUT
The @PUT annotation is a request method designator and corresponds to the similarly named HTTP method. The Java method annotated with this request method designator will process HTTP PUT requests. The behavior of a resource is determined by the HTTP method to which the resource is responding.
@DELETE
The @DELETE annotation is a request method designator and corresponds to the similarly named HTTP method. The Java method annotated with this request method designator will process HTTP DELETE requests. The behavior of a resource is determined by the HTTP method to which the resource is responding.
@HEAD
The @HEAD annotation is a request method designator and corresponds to the similarly named HTTP method. The Java method annotated with this request method designator will process HTTP HEAD requests. The behavior of a resource is determined by the HTTP method to which the resource is responding.
@PathParam
The @PathParam annotation is a type of parameter that you can extract for use in your resource class. URI path parameters are extracted from the request URI, and the parameter names correspond to the URI path template variable names specified in the @Path class-level annotation.
@QueryParam
The @QueryParam annotation is a type of parameter that you can extract for use in your resource class. Query parameters are extracted from the request URI query parameters.
@Consumes
The @Consumes annotation is used to specify the MIME media types of representations a resource can consume that were sent by the client.
@Produces
The @Produces annotation is used to specify the MIME media types of representations a resource can produce and send back to the client: for example, "text/plain".
@Provider
The @Provider annotation is used for anything that is of interest to the JAX-RS runtime, such as MessageBodyReader and MessageBodyWriter. For HTTP requests, the MessageBodyReader is used to map an HTTP request entity body to method parameters. On the response side, a return value is mapped to an HTTP response entity body by using a MessageBodyWriter. If the application needs to supply additional metadata, such as HTTP headers or a different status code, a method can return a Response that wraps the entity and that can be built using Response.ResponseBuilder.
@ApplicationPath
The @ApplicationPath annotation is used to define the URL mapping for the application. The path specified by @ApplicationPath is the base URI for all resource URIs specified by @Path annotations in the resource class. You may only apply @ApplicationPathto a subclass of javax.ws.rs.core.Application.

Tutorials:




Video