JAX-RS之jackson去处理json

  在JAX-RS中使用jackson去处理json，例子如下。下文讲解了，如何将一个对象转变为JSON对象，使用的是jackson。

1 放置resteasy-jackson-provider.jar

2
一个简单对象

public class Product {
 
	String name;
	int qty;
 
	public String getName() {
		return name;
	}
 
	public void setName(String name) {
		this.name = name;
	}
 
	public int getQty() {
		return qty;
	}
 
	public void setQty(int qty) {
		this.qty = qty;
	}
 
}

3 使用注解@Produces("application/json").就可以转换JSON了

import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Response;
 
@Path("/json/product")
public class JSONService {
 
	@GET
	@Path("/get")
	@Produces("application/json")
	public Product getProductInJSON() {
 
		Product product = new Product();
		product.setName("iPad 3");
		product.setQty(999);
 
		return product; 
 
	}
 
	@POST
	@Path("/post")
	@Consumes("application/json")
	public Response createProductInJSON(Product product) {
 
		String result = "Product created : " + product;
		return Response.status(201).entity(result).build();
 
	}
 
}

  注意，要把web.xml中的自动扫描注释掉，否则会出错：
<!-- disabled auto scan
        <context-param>
             <param-name>resteasy.scan</param-name>
             <param-value>true</param-value>
</context-param> -->

<context-param>
<param-name>resteasy.resources</param-name>
<param-value>com.mkyong.rest.JSONService</param-value>
</context-param>

4 客户端调用服务端的GET,用于将服务端的对象转为JSON,如下:
 

try {

			URL url = new URL(
					"http://localhost:8085/Resetjason/json/product/get");
			HttpURLConnection conn = (HttpURLConnection) url.openConnection();
			conn.setRequestMethod("GET");
			conn.setRequestProperty("Accept", "application/json");

			if (conn.getResponseCode() != 200) {
				throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
			}

			BufferedReader br = new BufferedReader(new InputStreamReader(
					(conn.getInputStream())));

			String output;
			System.out.println("Output from Server .... \n");
			while ((output = br.readLine()) != null) {

				System.out.println(output);
			}
			
			conn.disconnect();

		} catch (MalformedURLException e) {

			e.printStackTrace();
		} catch (IOException e) {

			e.printStackTrace();
			
		}

运行后,输出:
Output from Server ....

{"qty":999,"name":"iPad 3"}

5 调用服务端的POST,将JSON传入,看其如何转化位product
 

	try {

			URL url = new URL(
					"http://localhost:8085/Resetjason/json/product/post");
			HttpURLConnection conn = (HttpURLConnection) url.openConnection();
			conn.setDoOutput(true);
			conn.setRequestMethod("POST");
			conn.setRequestProperty("Content-Type", "application/json");

			String input = "{\"qty\":100,\"name\":\"iPad 4\"}";

			OutputStream os = conn.getOutputStream();
			os.write(input.getBytes());
			os.flush();

			if (conn.getResponseCode() != HttpURLConnection.HTTP_CREATED) {
				throw new RuntimeException("Failed : HTTP error code : "
						+ conn.getResponseCode());
			}

			BufferedReader br = new BufferedReader(new InputStreamReader(
					(conn.getInputStream())));

			String output;
			System.out.println("Output from Server .... \n");
			while ((output = br.readLine()) != null) {

				System.out.println(output);
			}

			conn.disconnect();

		} catch (MalformedURLException e) {

			e.printStackTrace();
		} catch (IOException e) {

			e.printStackTrace();

		}

	}

输出为:
  Output from Server ....

Product created : Product [name=iPad 4, qty=100]