为什么要使用JAX-RS/Jersey? [英] Why use JAX-RS / Jersey?
问题描述
对不起，这个问题听起来很愚蠢，但是在使用Jersey开发了我的一些RESTful服务之后，我问了自己一个问题-如果REST只是一个体系结构，而不是像SOAP这样的协议，为什么我们需要一个像JAX这样的规范-RS?
Sorry, this questions sounds silly, but after developing some of my RESTful services using Jersey, I asked myself the question -- If REST is just an architecture, and not a protocol like SOAP, why do we need a specification like JAX-RS?
我实际上在Google上搜索了诸如"servlet和HTTP上的RESTful服务之间的区别"之类的问题，并总结了社区的答案，我得到了:
I actually googled for questions like "What is the difference between servlets and RESTful services over HTTP" and to sum up the community answers, I got:
- RESTful服务开发(在Jersey上)是一种体系结构，其固有地使用servlet.
- Jersey之类的符合JAX-RS的工具可轻松地将XML/JSON数据编组/拆组，从而为开发人员提供了帮助.
- REST帮助我们以比普通servlet高效得多的方式使用GET/POST/PUT/DELETE.
根据这些答案，我想我是否编写了一个使用JAXB(用于处理自动序列化)的servlet，并且在我的servlet代码中有效地使用了GET/POST/PUT/DELETE，所以我没有使用类似的工具泽西岛，因此是JAX-RS.
According to these answers, I guess if I write a servlet which uses JAXB (for dealing with automatic serialization), and I efficiently use GET/POST/PUT/DELETE in my servlet code, I don't use a tool like Jersey, and hence JAX-RS.
我知道我在通过此声明时非常错误，请纠正我.
I know I am terribly wrong passing this statement, please correct me.
PS:当我不得不在PHP中开发一些RESTful服务时，实际上就产生了这种疑问.经过一些RESTful PHP代码后，我意识到它们只是相同的旧PHP脚本，带有一些用于处理XML/JSON的辅助方法.
PS: This doubt actually came in when I had to develop some RESTful services in PHP. After going on through some of the RESTful PHP codes, I realized they are just the same old PHP scripts, with some helper methods for handling XML/JSON.
推荐答案
为什么使用JAX-RS/Jersey?
Why use JAX-RS / Jersey?
简短回答
因为它使RESTful服务的开发更加容易.
Because it makes the development of RESTful services easier.
长期回答
JAX-RS是一个标准，可轻松创建可部署到任何Java应用程序服务器(包括GlassFish，WebLogic，WebSphere，JBoss等)的RESTful服务.
JAX-RS is a standard that makes it easy to create a RESTful service that can be deployed to any Java application server: GlassFish, WebLogic, WebSphere, JBoss, etc.
JAX-RS是Java EE的一部分，当JAX-RS与其他Java EE技术一起使用时，创建RESTful服务变得更加容易:
JAX-RS is part of Java EE, and when JAX-RS is used with other Java EE technologies it becomes even easier to create your RESTful service:
- EJB -会话bean用作服务实现，还处理事务语义.
- JAX-RS -用于将会话bean公开为RESTful服务
- JPA -用于将POJO持久化到数据库中.注意如何将EntityManager注入到会话bean中.
- JAXB -用于将POJO与XML相互转换(在GlassFish中，还可以用于将POJO与JSON相互转换).默认情况下，JAX-RS处理与JAXB实现的交互.
- EJB - A session bean is used as the service implementation and also handles the transaction semantics.
- JAX-RS - Used to expose the session bean as a RESTful service
- JPA - Used to persist the POJOs to the database. Note how the EntityManager is injected onto the session bean.
- JAXB - Used to convert the POJO to/from XML (in GlassFish it can also be used to convert the POJO to/from JSON). JAX-RS by default handles the interaction with the JAXB implementation.
JAX-RS服务示例
package org.example;
import java.util.List;
import javax.ejb.*;
import javax.persistence.*;
import javax.ws.rs.*;
import javax.ws.rs.core.MediaType;
@Stateless
@LocalBean
@Path("/customers")
public class CustomerService {
@PersistenceContext(unitName="CustomerService",
type=PersistenceContextType.TRANSACTION)
EntityManager entityManager;
@POST
@Consumes(MediaType.APPLICATION_XML)
public void create(Customer customer) {
entityManager.persist(customer);
}
@GET
@Produces(MediaType.APPLICATION_XML)
@Path("{id}")
public Customer read(@PathParam("id") long id) {
return entityManager.find(Customer.class, id);
}
@PUT
@Consumes(MediaType.APPLICATION_XML)
public void update(Customer customer) {
entityManager.merge(customer);
}
@DELETE
@Path("{id}")
public void delete(@PathParam("id") long id) {
Customer customer = read(id);
if(null != customer) {
entityManager.remove(customer);
}
}
@GET
@Produces(MediaType.APPLICATION_XML)
@Path("findCustomersByCity/{city}")
public List<Customer> findCustomersByCity(@PathParam("city") String city) {
Query query = entityManager.createNamedQuery("findCustomersByCity");
query.setParameter("city", city);
return query.getResultList();
}
}
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