无法反序列化java.util实例。ArrayList的VALUE_STRING

I have a REST service built with Jersey and deployed in the AppEngine. The REST service implements the verb PUT that consumes an application/json media type. The data binding is performed by Jackson.

我有一个与Jersey一起构建并部署在AppEngine中的REST服务。REST服务实现使用应用程序/json媒体类型的谓词PUT。数据绑定由Jackson执行。

The verb consumes an enterprise-departments relation represented in JSON as

谓词使用以JSON表示的企业部门关系。

{"name":"myEnterprise", "departments":["HR","IT","SC"]}

In the client side, I use gson to convert the JSON representation into a java object. Then, I pass the object to my REST service and it works fine.

在客户端，我使用gson将JSON表示转换为java对象。然后，我将对象传递给REST服务，它可以正常工作。

Problem:

问题:

When my JSON representation has only one item in the collection

当我的JSON表示在集合中只有一个项时

{"name":"myEnterprise", "departments":["HR"]}

the service cannot deserialize the object.

服务不能反序列化对象。

ATTENTION: /enterprise/enterprise: org.codehaus.jackson.map.JsonMappingException: 
Can not deserialize instance of java.util.ArrayList out of VALUE_STRING token at 
[Source: org.mortbay.jetty.HttpParser$Input@5a9c5842; line: 1, column: 2

As reported by other users, the solution is to add the flag ACCEPT_SINGLE_VALUE_AS_ARRAY (e.g., Jersey: Can not deserialize instance of ArrayList out of String). Nevertheless, I am not controlling an ObjectMapper because in the service side it is transparently made by Jackson.

正如其他用户所报告的，解决方案是添加flag ACCEPT_SINGLE_VALUE_AS_ARRAY(例如，Jersey:不能将ArrayList的实例从字符串中反序列化)。不过，我并没有控制ObjectMapper，因为在服务端，它是由Jackson透明制作的。

Question:

问题:

Is there a way to configure the ObjectMapper on the service side to enable ACCEPT_SINGLE_VALUE_AS_ARRAY? annotations? web.xml?

是否有办法在服务端配置ObjectMapper以启用ACCEPT_SINGLE_VALUE_AS_ARRAY?注释吗?web . xml ?

Code details

代码的细节

Java object:

Java对象:

@XmlRootElement
public class Enterprise {
    private String name;
    private List<String> departments;

    public Enterprise() {}

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public List<String> getDepartments() {
        return departments;
    }
    public void setDepartments(List<String> departments) {
        this.departments = departments;
    }
}

The REST service side:

其余服务端:

    @PUT
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    @Path("/enterprise") 
    public Response putEnterprise(Enterprise enterprise,
            @Context HttpServletRequest req){
         ...
    }

Client side:

客户端:

...
String jsonString = "{\"name\":\"myEnterprise\", \"departments\":[\"HR\"]}";
Enterprise enterprise = gson.fromJson(jsonString, Enterprise.class);
System.out.println(gson.toJson(enterprise));
response = webResource              
           .type(MediaType.APPLICATION_JSON)
           .put(ClientResponse.class,enterprise);
if (response.getStatus() >= 400) {
        throw new RuntimeException("Failed : HTTP error code : " + response.getStatus());
}
...

4 个解决方案

#1

This is the solution for my old question:

这是我的老问题的解决方案:

I implemented my own ContextResolver in order to enable the DeserializationConfig.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY feature.

为了启用DeserializationConfig.Feature，我实现了自己的上下文解决程序。ACCEPT_SINGLE_VALUE_AS_ARRAY特性。

package org.lig.hadas.services.mapper;

import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.ext.ContextResolver;
import javax.ws.rs.ext.Provider;

import org.codehaus.jackson.map.DeserializationConfig;
import org.codehaus.jackson.map.ObjectMapper;

@Produces(MediaType.APPLICATION_JSON)
@Provider
public class ObjectMapperProvider implements ContextResolver<ObjectMapper>
{
   ObjectMapper mapper;

   public ObjectMapperProvider(){
       mapper = new ObjectMapper();
       mapper.configure(DeserializationConfig.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);
   }
   @Override
   public ObjectMapper getContext(Class<?> type) {
       return mapper;
   }
}

And in the web.xml I registered my package into the servlet definition...

和网络。我将我的包注册到servlet定义中…

<servlet>
    <servlet-name>...</servlet-name>
    <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
    <init-param>
        <param-name>com.sun.jersey.config.property.packages</param-name>
        <param-value>...;org.lig.hadas.services.mapper</param-value>        
    </init-param>
    ...
</servlet>

... all the rest is transparently done by jersey/jackson.

…剩下的都是由泽西/杰克逊做的。

#2

do you try

你试一试

[{"name":"myEnterprise", "departments":["HR"]}]

the square brace is the key point.

方括号是关键。

#3

Setting this attribute to ObjectMapper instance works,

将此属性设置为ObjectMapper实例有效，

objectMapper.enable(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY);

#4

For people that find this question by searching for the error message, you can also see this error if you make a mistake in your @JsonProperty annotations such that you annotate a List-typed property with the name of a single-valued field:

对于通过搜索错误消息找到这个问题的人，如果您在@JsonProperty注释中犯了错误，您也可以看到这个错误，这样您就可以用一个单值字段的名称来注释一个列表类型的属性:

@JsonProperty("someSingleValuedField") // Oops, should have been "someMultiValuedField"
public List<String> getMyField() { // deserialization fails - single value into List
  return myField;
}

#1