Spring REST 服务:如何配置以删除 json 响应中的空对象 [英] Spring REST Service: how to configure to remove null objects in json response

问题描述

我有一个返回 json 响应的 spring 网络服务.我正在使用此处给出的示例来创建服务:http://www.mkyong.com/spring-mvc/spring-3-mvc-and-json-example/

I have a spring webservice that returns a json response. I'm using the example given here to create the service: http://www.mkyong.com/spring-mvc/spring-3-mvc-and-json-example/

返回的json格式为:{"name":null,"staffName":["kfc-kampar","smith"]}

The format the json is returned in is: {"name":null,"staffName":["kfc-kampar","smith"]}

我想从返回的响应中删除任何空对象，使其看起来像这样:{"staffName":["kfc-kampar","smith"]}

I want to remove any null objects from the returned response so it looks like this: {"staffName":["kfc-kampar","smith"]}

我在这里发现了类似的问题，但我已经找到了一个有效的解决方案，例如

I've found similar questions asked here but I've been able to get a solution working e.g.

在 Spring 中配置 ObjectMapper

如何在使用基于 spring 注释的配置时配置 MappingJacksonHttpMessageConverter?

配置 jacksonObjectMapper 在 spring mvc 3 中不起作用

如何将 spring mvc 3 配置为不返回null"json 响应中的对象?

Spring 配置@ResponseBody JSON 格式

Jackson+Spring3.0.5 自定义对象映射器

通过阅读这些和其他来源，我认为实现我想要的最简洁的方法是使用 Spring 3.1 和可以在 mvc-annotation 中配置的消息转换器.我更新的 spring 配置文件是:

From reading through these and other sources, I figured the cleanest way to achieve what I wanted was to use Spring 3.1 and the message-converters that can be configured within the mvc-annotation. My updated spring config file is:

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
    http://www.springframework.org/schema/beans     
    http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
    http://www.springframework.org/schema/context 
    http://www.springframework.org/schema/context/spring-context-3.1.xsd
    http://www.springframework.org/schema/mvc
    http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd">

<context:component-scan base-package="com.mkyong.common.controller" />

<mvc:annotation-driven>
    <mvc:message-converters>
        <bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
            <property name="prefixJson" value="true" />
            <property name="supportedMediaTypes" value="application/json" />
            <property name="objectMapper">
                <bean class="org.codehaus.jackson.map.ObjectMapper">
                    <property name="serializationInclusion" value="NON_NULL"/>
                </bean>
            </property>
        </bean>
    </mvc:message-converters>
</mvc:annotation-driven>

服务类与 mkyong.com 站点上给出的相同，只是我注释掉了 Shop name 变量的设置，因此它为空，即

The service class is the same as given on the mkyong.com site, except I commented out the setting of the Shop name variable so it's null i.e.

@Controller
@RequestMapping("/kfc/brands")
public class JSONController {
    @RequestMapping(value="{name}", method = RequestMethod.GET)
    @ResponseStatus(HttpStatus.OK) 
    public @ResponseBody Shop getShopInJSON(@PathVariable String name) {
        Shop shop = new Shop();
        //shop.setName(name);
        shop.setStaffName(new String[]{name, "cronin"});
        return shop;
    }
}

我使用的 Jackson jar 是 jackson-mapper-asl 1.9.0 和 jackson-core-asl 1.9.0.这些是我添加到 pom 中的唯一新 jar，作为我从 mkyong.com 下载的 spring-json 项目的一部分.

The Jackson jars I'm using are jackson-mapper-asl 1.9.0 and jackson-core-asl 1.9.0. These are the only new jars I've added to the pom as provided as part of the spring-json project I downloaded from mkyong.com.

项目构建成功，但是当我通过浏览器调用服务时，我仍然得到相同的结果，即{"name":null,"staffName":["kfc-kampar","smith"]}

The project builds successfully, but when I invoke the service through the browser I still get the same thing i.e. {"name":null,"staffName":["kfc-kampar","smith"]}

谁能告诉我我的配置哪里出了问题?

Can anyone tell me where I'm going wrong with my configuration?

我尝试了其他几个选项，但我能够以正确格式返回 json 的唯一方法是将对象映射器添加到 JSONController 并让getShopInJSON"方法返回一个字符串，即

I've tried several other options, but the only way I've been able to return the json in the correct format is to add the Object mapper to the JSONController and have the "getShopInJSON" method return a string i.e.

public @ResponseBody String getShopInJSON(@PathVariable String name) throws JsonGenerationException, JsonMappingException, IOException {
    ObjectMapper mapper = new ObjectMapper();
    mapper.setSerializationInclusion(JsonSerialize.Inclusion.NON_NULL);

    Shop shop = new Shop();
    //shop.setName(name);
    shop.setStaffName(new String[]{name, "cronin"});
    String test = mapper.writeValueAsString(shop);
    return test;
}

现在，如果我调用该服务，我会得到预期的结果，即{"staffName":["kfc-kampar","cronin"]}

Now if I invoke the service I get the expected i.e. {"staffName":["kfc-kampar","cronin"]}

我也可以使用 @JsonIgnore 注释让它工作，但是这个解决方案不适合我.

I've also been able to get it to work using the @JsonIgnore annotation, but this solution isn't suitable for me.

我不明白为什么它在代码中有效，但在配置中无效，所以任何帮助都会很棒.

I don't understand why it's working in code but not in the configuration, so any help would be fantastic.

推荐答案

从 Jackson 2.0 开始你可以使用 JsonInclude

Since Jackson 2.0 you can use JsonInclude

@JsonInclude(Include.NON_NULL)
public class Shop {
    //...
}

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