android - HttpMessageNotReadableException : Could not read JSON: Unrecognized field using Spring for Android

Question

我正在开发与我的服务器通信的 Android 应用程序。

这种通信是通过 Spring 框架和 Jackson 完成的。

我已成功向我的服务器发送请求，但没有收到响应。

这是我所做的:

安卓应用:

public Loja getLoja() {
    RestTemplate restTemplate = new RestTemplate();
    restTemplate.getMessageConverters().add(
                 new MappingJacksonHttpMessageConverter());
    restTemplate.setRequestFactory(new HttpComponentsClientHttpRequestFactory());
    String url = BASE_URL + "/android/played.json";
    return restTemplate.getForObject(url, Loja.class);
}

Loja.class 我有它的两个版本(Android 和 Server 中的其他版本。它们完全一样:

public class Loja {

    private String nome;
    private String xValue;
    private String yValue;
    private String andar;
    
    public Loja(String nome, String xValue, String yValue, String andar) {
        this.nome = nome;
        this.xValue = xValue;
        this.yValue = yValue;
        this.andar = andar;
    }
    
    public Loja() {
    }

    public String getAndar() {
        return andar;
    }

    public void setAndar(String andar) {
        this.andar = andar;
    }

    public String getNome() {
        return nome;
    }

    public void setNome(String nome) {
        this.nome = nome;
    }

    public String getxValue() {
        return xValue;
    }

    public void setxValue(String xValue) {
        this.xValue = xValue;
    }

    public String getyValue() {
        return yValue;
    }

    public void setyValue(String yValue) {
        this.yValue = yValue;
    }

}

这是我的 Controller :

@RequestMapping("/android/played")
public ModelAndView getLoja() {
    System.out.println("Android Resquest.");
    Loja loja = new Loja("teste", "20", "30", "1");
    ModelAndView mav = new ModelAndView();
    mav.addObject("Loja", loja);
    return mav;
}

有了这一切，我在 Android 应用程序中遇到了以下异常:

03-21 22:13:06.197: E/AndroidRuntime(25342): java.lang.RuntimeException: An error occured while executing doInBackground()03-21 22:13:06.197: E/AndroidRuntime(25342): at android.os.AsyncTask$3.done(AsyncTask.java:299)03-21 22:13:06.197: E/AndroidRuntime(25342): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)03-21 22:13:06.197: E/AndroidRuntime(25342): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)03-21 22:13:06.197: E/AndroidRuntime(25342): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)03-21 22:13:06.197: E/AndroidRuntime(25342): at java.util.concurrent.FutureTask.run(FutureTask.java:137)03-21 22:13:06.197: E/AndroidRuntime(25342): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)03-21 22:13:06.197: E/AndroidRuntime(25342): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)03-21 22:13:06.197: E/AndroidRuntime(25342): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)03-21 22:13:06.197: E/AndroidRuntime(25342): at java.lang.Thread.run(Thread.java:856)03-21 22:13:06.197: E/AndroidRuntime(25342): Caused by: org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Unrecognized field "Loja" (Class com.example.androidspring.Loja), not marked as ignorable03-21 22:13:06.197: E/AndroidRuntime(25342): at [Source: org.apache.http.conn.EofSensorInputStream@422e3c58; line: 1, column: 10] (through reference chain: com.example.androidspring.Loja["Loja"]); nested exception is org.codehaus.jackson.map.exc.UnrecognizedPropertyException: Unrecognized field "Loja" (Class com.example.androidspring.Loja), not marked as ignorable03-21 22:13:06.197: E/AndroidRuntime(25342): at [Source: org.apache.http.conn.EofSensorInputStream@422e3c58; line: 1, column: 10] (through reference chain: com.example.androidspring.Loja["Loja"])03-21 22:13:06.197: E/AndroidRuntime(25342): at org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.readInternal(MappingJacksonHttpMessageConverter.java:125)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.springframework.http.converter.AbstractHttpMessageConverter.read(AbstractHttpMessageConverter.java:147)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:76)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:484)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:439)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:237)03-21 22:13:06.197: E/AndroidRuntime(25342): at com.example.androidspring.MainActivity.getLoja(MainActivity.java:59)03-21 22:13:06.197: E/AndroidRuntime(25342): at com.example.androidspring.MainActivity$DownloadFilesTask.doInBackground(MainActivity.java:72)03-21 22:13:06.197: E/AndroidRuntime(25342): at com.example.androidspring.MainActivity$DownloadFilesTask.doInBackground(MainActivity.java:1)03-21 22:13:06.197: E/AndroidRuntime(25342): at android.os.AsyncTask$2.call(AsyncTask.java:287)03-21 22:13:06.197: E/AndroidRuntime(25342): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)03-21 22:13:06.197: E/AndroidRuntime(25342): ... 5 more03-21 22:13:06.197: E/AndroidRuntime(25342): Caused by: org.codehaus.jackson.map.exc.UnrecognizedPropertyException: Unrecognized field "Loja" (Class com.example.androidspring.Loja), not marked as ignorable03-21 22:13:06.197: E/AndroidRuntime(25342): at [Source: org.apache.http.conn.EofSensorInputStream@422e3c58; line: 1, column: 10] (through reference chain: com.example.androidspring.Loja["Loja"])03-21 22:13:06.197: E/AndroidRuntime(25342): at org.codehaus.jackson.map.deser.StdDeserializationContext.unknownFieldException(StdDeserializationContext.java:267)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.codehaus.jackson.map.deser.std.StdDeserializer.reportUnknownProperty(StdDeserializer.java:649)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.codehaus.jackson.map.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:635)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.codehaus.jackson.map.deser.BeanDeserializer.handleUnknownProperty(BeanDeserializer.java:1355)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:717)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:580)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2723)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1914)03-21 22:13:06.197: E/AndroidRuntime(25342): at org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.readInternal(MappingJacksonHttpMessageConverter.java:122)03-21 22:13:06.197: E/AndroidRuntime(25342): ... 15 more

据我所知，它无法识别我的 Loja 类(class)。

但它们完全一样!还能是什么？

Answer 1

该异常似乎表明当 Jackson 映射器试图创建一个 Loja从返回的 json 中，遇到了一个 key 为 Loja 的 json 字段，它不知道如何处理(因为 Loja 名为“Loja”的 java 对象中没有字段)，所以它失败了。这似乎是合乎逻辑的，因为服务器似乎有效地返回了这个 json 结构:

{"Loja":{"nome":"teste","xValue":"20","yValue":"30","andar":"1"}}

因此，您有两个主要选择。

1. 更改传递给 getForObject() 的对象或
2. 更改从服务器返回的 json。

对于第一个，您可以让您的客户做 getForObject()传入 Object包含 Loja .

类似这样的类:

class MyObj {
    private Loja Loja;

    public void setLoja(Loja loja) {
        this.Loja = loja;
    }

    public Loja getLoja() {
        return this.Loja;
    }
}

正在与此调用一起使用:

restTemplate.getForObject(url, MyObj.class);

或者，您可以让您的服务器返回 Loja objects 字段作为模型的一部分，或者更好的是，返回 Loja 的实例您创建的对象。 Spring 足够聪明，可以利用 Jackson 将您的 POJO 转换为您期望的正确 json 模型。

@RequestMapping("/android/played")
public Loja getLoja() {
    System.out.println("Android Resquest.");

    return new Loja("teste", "20", "30", "1");
}

这会产生这个 json:

{"nome":"teste","xValue":"20","yValue":"30","andar":"1"}

您的getForObject() 可以阅读客户端上的方法就是它当前的方式。