笔记：Jersey REST 传输格式-JSON

Posted 2020-09-26 追寻自由的路途

JSON 类型已经成为Ajax技术中数据传输的实际标准，Jersey 提供了多种处理JSON数据的包和解析方式，下表展示了JSON包和解析方式：

解析方式\JSON支持包	MOXy	JSON-P	Jackson
基于POJO的JSON绑定	是	否	是
基于JAXB的JSON绑定	是	否	是
低级的（逐字的）JSON解析和处理	否	是	否

1. 使用 MOXy 处理JSON

   MOXy 是 EclipseLink项目的一个模块，是使用JAXB和SDO作为XML绑定的技术基础，实现了JSR222标准（JAXB2.2）和JSR235标准（SDO2.11），使用MOXy的Java开发者能够高效的完成Java类和XML绑定，所要的只是使用注解来定义他们之间的关系，同时，MOXy实现了JSR-353标准（Java API for Processing JSON1.0），以JAXB为基础来实现对JSR353的支持

• 定义依赖

  <dependency>

  ??????????<groupId>org.glassfish.jersey.media</groupId>

  ??????????<artifactId>jersey-media-moxy</artifactId>

  </dependency>

• 定义Application

  // 该注解用于Servlet3

  @ApplicationPath("/api/*")

  public class JsonResourceConfig extends ResourceConfig {

  ????????public JsonResourceConfig() {

  ??????????????? ?register(MyResource.class);

  // 注册JSON处理

  register(MOXyJsonProvider.class);

  ??????? property(CommonProperties.MOXY_JSON_FEATURE_DISABLE, Boolean.TRUE);

  ???????????????? System.out.println("JsonResourceConfig 构造函数调用");

  ????????}

  }

• Servlet配置（Servlet3 可以不定义web.xml配置）

  <?xml version="1.0" encoding="UTF-8"?>

  <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

  ??????????????????xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

  ????????<servlet>

  ????????????????<servlet-name>Jersey Web Application</servlet-name>

  ????????????????<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>

  ????????????????<init-param>

  ????????????????????????<param-name>javax.ws.rs.Application</param-name>

  ????????????????????????<param-value>org.drsoft.rest.JsonResourceConfig</param-value>

  ????????????????</init-param>

  ????????????????<load-on-startup>1</load-on-startup>

  ????????</servlet>

  ????????<servlet-mapping>

  ????????????????<servlet-name>Jersey Web Application</servlet-name>

  ????????????????<url-pattern>/*</url-pattern>

  ????????</servlet-mapping>

  </web-app>

• REST服务代码

????????@GET

????????@Path ("book")

????????@Produces (MediaType.APPLICATION_JSON)

????????@Consumes (MediaType.APPLICATION_JSON)

????????public Book getBook() {

????????????????Book newBook = new Book();

????????????????newBook.setId(1);

????????????????newBook.setName("Java RESTful WebService学习");

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????????????????Publisher newPublisher = new Publisher();

????????????????newPublisher.setName("机械出版社");

????????????????newPublisher.setIsbn("989797397342343");

????????????????newPublisher.setPublishTime(new Date());

????????????????newBook.setPublisher(newPublisher);

? ?

????????????????return newBook;

????????}

其中Book类和Publisher类不需要额外处理，MOXy可以根据POJO类来进行JSON绑定，如果需要使用 JAXB 注解本身可以控制一定 JSON 格式输出，具体来说,直接通过使用 JAXB 注释很容易做到重命名(@XmlElement)和删除(@XmlTransient)属性，示例代码如下：

@XmlRootElement

public class Publisher {

????????@XmlElement (name = "n")

????????private String name;

????????private String isbn;

????????private Date publishTime;

????????@XmlTransient

????????public Date getPublishTime() {

????????????????return publishTime;

????????}

????????public void setPublishTime(Date publishTime) {

????????????????this.publishTime = publishTime;

????????}

// setter 和 getter 方法

}

JSON输出内容如下：

{

????????"n": "机械出版社",

????????"isbn": "989797397342343"

}

? ?

1. 使用JSON-P处理JSON

   JSON-P的全称是Java API for JSON Processing（Java 的JSON处理API），是JSR353标准规范，用于统一Java处理JSON格式数据的API，其生产和消费的JSON数据以流的形式处理，并为JSON数据建立Java对象模型。

• 定义依赖

  <dependency>

  ????????????<groupId>org.glassfish.jersey.media</groupId>

  ????????????<artifactId>jersey-media-json-processing</artifactId>

  </dependency>

• 定义Application

  // 该注解用于Servlet3

  @ApplicationPath("/api/*")

  public class JsonProcessingResourceConfig extends ResourceConfig {

  ????????public JsonProcessingResourceConfig() {

  ????????????????// 注册REST类

  ????????????????register(MyResource.class);

  ????????????????// 启用格式化Json数据的输出

  ????????????????property(JsonGenerator.PRETTY_PRINTING, Boolean.TRUE);

  ????????}

  }

• Servlet配置（Servlet3 可以不定义web.xml配置）

  <?xml version="1.0" encoding="UTF-8"?>

  <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

  ??????????????????xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

  ????????<servlet>

  ????????????????<servlet-name>Jersey Web Application</servlet-name>

  ????????????????<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>

  ????????????????<init-param>

  ????????????????????????<param-name>javax.ws.rs.Application</param-name>

  ????????????????????????<param-value>org.drsoft.rest.JsonProcessingResourceConfig</param-value>

  ????????????????</init-param>

  ????????????????<load-on-startup>1</load-on-startup>

  ????????</servlet>

  ????????<servlet-mapping>

  ????????????????<servlet-name>Jersey Web Application</servlet-name>

  ????????????????<url-pattern>/*</url-pattern>

  ????????</servlet-mapping>

  </web-app>

• REST服务代码

????????@GET

????????@Path ("bookJsonP")

????????@Produces (MediaType.APPLICATION_JSON+";charset=UTF-8")

????????@Consumes (MediaType.APPLICATION_JSON)

????????public JsonObject getBookByJsonP() {

? ?

????????????????JsonObjectBuilder publisherObjectBuilder = Json.createObjectBuilder();

????????????????publisherObjectBuilder.add("isbn", "939393939393939");

????????????????publisherObjectBuilder.add("name", "电子工程也出版社");

????????????????publisherObjectBuilder.add("publishTime", new Date().toString());

? ?

????????????????JsonObjectBuilder objectBuilder = Json.createObjectBuilder();

????????????????objectBuilder.add("name", "Java RESTful WebService学习");

????????????????objectBuilder.add("id", 999);

????????????????objectBuilder.add("publisher", publisherObjectBuilder);

? ?

????????????????return objectBuilder.build();

????????}

JSON-P不需要创建POJO类，通过JsonObjectBuilder来创建JsonObject对象，通过该对象输出Json字符串。

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