处理从 REST Spring MVC 方法返回的 JSON 时的 HTTP GET 问题

Question

我在 Spring MVC 控制器中有一个方法如下：

// Gets a Person via REST.

@RequestMapping(value="/person/{personId}", method=RequestMethod.GET)
public ModelAndView getPerson(@PathVariable("personId") String personId) {

    logger.info(RestController.class.getName() + ".getPerson() method called."); 

    Person person = personService.get(Integer.parseInt(personId));
    return new ModelAndView(view,"person", person);        
} 

该方法工作正常，但在客户端处理 JSON 的代码中，出现以下异常：

无法识别的字段“person”（类库App.model.Person），未标记为可忽略（6 个已知属性：、“personId”、“address”、“telephone”、“books”、“name”、“email” ])

代码如下：

// Set request.
        String url = ("http://localhost:8080/Library/rest/person/1");      
        HttpGetRequest httpGetRequest = new HttpGetRequest(url, "GET", ""); 

        // Make request.
        httpGetRequest.get();

// Get response.        
        if (httpGetRequest.getResponseCode() != 200) {                  
            throw new RuntimeException("Get request failed: HTTP error code: " + httpGetRequest.getResponseCode());
        } 
        else {                                      

            // Receive JSON from server and convert to Person.
            ObjectMapper mapper = new ObjectMapper(); 
            Person person = mapper.readValue(httpGetRequest.getResponse(), Person.class);
            System.out.println("Person:");
            System.out.println(person.toString());
            if (! (person.getBooks().isEmpty())) {
                System.out.println("Books:");
                for (Book book : person.getBooks()) {
                    System.out.println(book.toString());
                }
            }
        }

Person 是一个简单的 POJO，如下：

public class Person implements Serializable {

// Attributes.        
private Integer personId;        
private String name;  
private String address;   
private String telephone;       
private String email;        
private List<Book> books;

我正在使用 ModelAndView 构造函数，ModelAndView(String viewName, String modelName, Object modelObject)。所以根据 JavaDoc 我必须指定一个 modelName 但我该如何在客户端处理这个？

现在，如果我在以下代码中使用名为 Messages 的类，则客户端没有收到以下响应：

ObjectMapper mapper = new ObjectMapper(); 
            Object obj =  mapper.readValue(httpGetRequest.getResponse(), Object.class);
            if (obj instanceof Messages) {
              Messages m = (Messages) obj;
              for (String s : m.getMessages())
                  System.out.println("Here " + s);


            }

Messages 是一个实用程序类：

public class Messages {

private List<String> messages;

public Messages() { 
    messages = new ArrayList<String>();
}

现在使用控制器方法：

@RequestMapping(value="/person/{personId}", method=RequestMethod.GET)

@ResponseBody 公共字符串 getPerson(@PathVariable("personId") String personId) {

logger.info(RestController.class.getName() + ".getPerson() method called."); 

Person person = personService.get(Integer.parseInt(personId));

ObjectMapper mapper = new ObjectMapper();
try {
    Messages m = new Messages();
    m.addMessage("SDGSFGSDFGSDFASDG");
    return mapper.writeValueAsString(m);
    // return mapper.writeValueAsString(person);
}
catch (JsonProcessingException ex) {

        return null;
 }

}

记录客户端，我得到：

Sending Get request: http://localhost:8080/Library/rest/person/1.

接收响应代码：200。 {消息=[SDGSFGSDFGSDFASDG]}

Answer 1

如果您的 GET 调用没有重定向，请尝试以下操作：

@RequestMapping(value="/person/{personId}", method=RequestMethod.GET)
@ResponseBody
public String getPerson(@PathVariable("personId") String personId) {

    logger.info(RestController.class.getName() + ".getPerson() method called."); 

    Person person = personService.get(Integer.parseInt(personId));

    ObjectMapper mapper = new ObjectMapper();
    return mapper.writeValueAsString(person);

}

确保Messages 类也是 POJO

public class Messages implements Serializable{

private List<String> messages;

//setters and getters for messages

}