在 Spring 中配置 ObjectMapper

Question

我的目标是配置objectMapper，使其仅序列化用@JsonProperty注释的元素。

为此，我遵循了说明，其中说明了如何配置对象映射器。

我按照此处所述添加了自定义对象映射器。

但是，当类 NumbersOfNewEvents 被序列化时，它仍然包含 json 中的所有属性。

为什么会发生这种情况，我怎样才能得到想要的结果？

杰克逊1.8.0 spring 3.0.5

CustomObjectMapper

public class CompanyObjectMapper extends ObjectMapper {
    public CompanyObjectMapper() {
        super();
        setVisibilityChecker(getSerializationConfig()
                .getDefaultVisibilityChecker()
                .withCreatorVisibility(JsonAutoDetect.Visibility.NONE)
                .withFieldVisibility(JsonAutoDetect.Visibility.NONE)
                .withGetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withIsGetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withSetterVisibility(JsonAutoDetect.Visibility.DEFAULT));
    }
}

servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

    <context:component-scan base-package="de.Company.backend.web" />
 
    <mvc:annotation-driven />
    
    <bean
        class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
        <property name="messageConverters">
            <list>
                <bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
                    <property name="objectMapper" ref="jacksonObjectMapper" />
                </bean>
            </list>
        </property>
    </bean>
    
    <bean id="jacksonObjectMapper" class="de.Company.backend.web.CompanyObjectMapper" />
</beans>

NumbersOfNewEvents

public class NumbersOfNewEvents implements StatusAttribute {

    public Integer newAccepts;
    public Integer openRequests;
    
    public NumbersOfNewEvents() {
        super();
    }
}

Answer 1

使用 Spring Boot (1.2.4) 和 Jackson (2.4.6)，以下基于注释的配置对我有用。

@Configuration
public class JacksonConfiguration {

    @Bean
    public ObjectMapper objectMapper() {
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        mapper.configure(MapperFeature.DEFAULT_VIEW_INCLUSION, true);

        return mapper;
    }
}

Answer 2

这可能是因为我使用的是 Spring 3.1（而不是您指定的问题所指定的 Spring 3.0.5），但 Steve Eastwood 的答案对我不起作用。此解决方案适用于 Spring 3.1：

在您的 spring xml 上下文中：

<mvc:annotation-driven>
    <mvc:message-converters>
        <bean class="org.springframework.http.converter.StringHttpMessageConverter"/>
        <bean class="org.springframework.http.converter.ByteArrayHttpMessageConverter"/>
        <bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
            <property name="objectMapper" ref="jacksonObjectMapper" />
        </bean>        
    </mvc:message-converters>
</mvc:annotation-driven>

<bean id="jacksonObjectMapper" class="de.Company.backend.web.CompanyObjectMapper" />

Answer 3

很长一段时间都有org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean。从 Spring Boot 1.2 版本开始，有用于 Java 配置的 org.springframework.http.converter.json.Jackson2ObjectMapperBuilder 。

在 String Boot 中，配置可以非常简单：

spring.jackson.deserialization.<feature_name>=true|false
spring.jackson.generator.<feature_name>=true|false
spring.jackson.mapper.<feature_name>=true|false
spring.jackson.parser.<feature_name>=true|false
spring.jackson.serialization.<feature_name>=true|false
spring.jackson.default-property-inclusion=always|non_null|non_absent|non_default|non_empty

在 classpath:application.properties 中或 @Configuration 类中的一些 Java 代码：

@Bean
public Jackson2ObjectMapperBuilder jacksonBuilder() {
    Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
    builder.indentOutput(true).dateFormat(new SimpleDateFormat("yyyy-MM-dd"));
    return builder;
}

请参阅：

• 官方文档 74.3 自定义 Jackson ObjectMapper< /a>
• https://dzone.com/articles/latest-jackson-integration
• 如何全局设置 Jackson 忽略其中的未知属性春天？
• http://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/http/converter/json/Jackson2ObjectMapperFactoryBean.html

Answer 4

我已将其与 Jackson 2.x 和 Spring 3.1.2+ 一起使用

servlet-context.xml:

请注意，根元素是 < code>，因此您可能需要删除 beans 并向其中一些元素添加 mvc，具体取决于您的设置。

    <annotation-driven>
        <message-converters>
            <beans:bean
                class="org.springframework.http.converter.StringHttpMessageConverter" />
            <beans:bean
                class="org.springframework.http.converter.ResourceHttpMessageConverter" />
            <beans:bean
                class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <beans:property name="objectMapper" ref="jacksonObjectMapper" />
            </beans:bean>
        </message-converters>
    </annotation-driven>

    <beans:bean id="jacksonObjectMapper"
        class="au.edu.unimelb.atcom.transfer.json.mappers.JSONMapper" />

au.edu.unimelb.atcom.transfer.json.mappers.JSONMapper.java：

public class JSONMapper extends ObjectMapper {

    public JSONMapper() {
        SimpleModule module = new SimpleModule("JSONModule", new Version(2, 0, 0, null, null, null));
        module.addSerializer(Date.class, new DateSerializer());
        module.addDeserializer(Date.class, new DateDeserializer());
        // Add more here ...
        registerModule(module);
    }

}

DateSerializer.java：

public class DateSerializer extends StdSerializer<Date> {

    public DateSerializer() {
        super(Date.class);
    }

    @Override
    public void serialize(Date date, JsonGenerator json,
            SerializerProvider provider) throws IOException,
            JsonGenerationException {
        // The client side will handle presentation, we just want it accurate
        DateFormat df = StdDateFormat.getBlueprintISO8601Format();
        String out = df.format(date);
        json.writeString(out);
    }

}

DateDeserializer.java：

public class DateDeserializer extends StdDeserializer<Date> {

    public DateDeserializer() {
        super(Date.class);
    }

    @Override
    public Date deserialize(JsonParser json, DeserializationContext context)
            throws IOException, JsonProcessingException {
        try {
            DateFormat df = StdDateFormat.getBlueprintISO8601Format();
            return df.parse(json.getText());
        } catch (ParseException e) {
            return null;
        }
    }

}

Answer 5

解决方案 1

第一个（经过测试的）工作解决方案非常有用，尤其是在使用 @EnableWebMvc 时：

@Configuration
@EnableWebMvc
public class WebConfig implements WebMvcConfigurer {
    @Autowired
    private ObjectMapper objectMapper;// created elsewhere
    @Override
    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
        // this won't add a 2nd MappingJackson2HttpMessageConverter 
        // as the SOLUTION 2 is doing but also might seem complicated
        converters.stream().filter(c -> c instanceof MappingJackson2HttpMessageConverter).forEach(c -> {
            // check default included objectMapper._registeredModuleTypes,
            // e.g. Jdk8Module, JavaTimeModule when creating the ObjectMapper
            // without Jackson2ObjectMapperBuilder
            ((MappingJackson2HttpMessageConverter) c).setObjectMapper(this.objectMapper);
        });
    }

解决方案 2

当然，下面的常见方法也适用（也可以与@EnableWebMvc):

@Configuration
@EnableWebMvc
public class WebConfig implements WebMvcConfigurer {
    @Autowired
    private ObjectMapper objectMapper;// created elsewhere
    @Override
    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
        // this will add a 2nd MappingJackson2HttpMessageConverter 
        // (additional to the default one) but will work and you 
        // won't lose the default converters as you'll do when overwriting
        // configureMessageConverters(List<HttpMessageConverter<?>> converters)
        // 
        // you still have to check default included
        // objectMapper._registeredModuleTypes, e.g.
        // Jdk8Module, JavaTimeModule when creating the ObjectMapper
        // without Jackson2ObjectMapperBuilder
        converters.add(new MappingJackson2HttpMessageConverter(this.objectMapper));
    }

为什么 @EnableWebMvc 的使用是一个问题？

@EnableWebMvc 正在使用DelegatingWebMvcConfiguration 扩展了 WebMvcConfigurationSupport ，它执行以下操作：

if (jackson2Present) {
    Jackson2ObjectMapperBuilder builder = Jackson2ObjectMapperBuilder.json();
    if (this.applicationContext != null) {
        builder.applicationContext(this.applicationContext);
    }
    messageConverters.add(new MappingJackson2HttpMessageConverter(builder.build()));
}

这意味着无法注入您自己的 ObjectMapper 来准备将其用于使用@EnableWebMvc时创建默认的MappingJackson2HttpMessageConverter。

Answer 6

我现在找到了基于 https://github.com/FasterXML/jackson-module-hibernate< 的解决方案/a>

我扩展了对象映射器并在继承的构造函数中添加了属性。

然后新的对象映射器被注册为一个bean。

<!-- https://github.com/FasterXML/jackson-module-hibernate -->
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    <property name="messageConverters">
        <array>
            <bean id="jsonConverter"
            class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
                <property name="objectMapper">
                    <bean class="de.company.backend.spring.PtxObjectMapper"/>
                </property>
            </bean>
        </array>
    </property>
</bean>   

Answer 7

如果您想添加自定义 ObjectMapper 来注册自定义序列化器，请尝试我的答案。

就我而言（Spring 3.2.4 和 Jackson 2.3.1），自定义序列化器的 XML 配置：

<mvc:annotation-driven>
    <mvc:message-converters register-defaults="false">
        <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
            <property name="objectMapper">
                <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                    <property name="serializers">
                        <array>
                            <bean class="com.example.business.serializer.json.CustomObjectSerializer"/>
                        </array>
                    </property>
                </bean>
            </property>
        </bean>
    </mvc:message-converters>
</mvc:annotation-driven>

以无法解释的方式被某些东西覆盖回默认值。

这对我有用：

CustomObject.java

@JsonSerialize(using = CustomObjectSerializer.class)
public class CustomObject {

    private Long value;

    public Long getValue() {
        return value;
    }

    public void setValue(Long value) {
        this.value = value;
    }
}

CustomObjectSerializer.java

public class CustomObjectSerializer extends JsonSerializer<CustomObject> {

    @Override
    public void serialize(CustomObject value, JsonGenerator jgen,
        SerializerProvider provider) throws IOException,JsonProcessingException {
        jgen.writeStartObject();
        jgen.writeNumberField("y", value.getValue());
        jgen.writeEndObject();
    }

    @Override
    public Class<CustomObject> handledType() {
        return CustomObject.class;
    }
}

我的解决方案中不需要 XML 配置 ((...)) 。

Answer 8

我正在使用 Spring 4.1.6 和 Jackson FasterXML 2.1.4。

    <mvc:annotation-driven>
        <mvc:message-converters>
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <property name="objectMapper">
                    <bean class="com.fasterxml.jackson.databind.ObjectMapper">
                        <!-- 设置不输出null字段-->
                        <property name="serializationInclusion" value="NON_NULL"/>
                    </bean>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>

这适用于我的 applicationContext.xml 配置

Answer 9

要在普通的 spring-web 中配置消息转换器，在本例中要启用 Java 8 JSR-310 JavaTimeModule，您首先需要在 @Configuration 类中实现 WebMvcConfigurer 并然后覆盖 configureMessageConverters 方法：

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json().modules(new JavaTimeModule(), new Jdk8Module()).build()
            .configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
    converters.add(new MappingJackson2HttpMessageConverter(objectMapper));
}

像这样，您可以在基于 Java 的 Spring 配置中注册任何自定义的 ObjectMapper 。

Answer 10

在 Spring Boot 2.2.x 中，您需要像这样配置它：

@Bean
public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder) {
    return builder.build()
}

Kotlin：

@Bean
fun objectMapper(builder: Jackson2ObjectMapperBuilder) = builder.build()

Answer 11

在 Spring 4 以上，如果您只想配置 ObjectMapper，则无需配置 MappingJacksonHttpMessageConverter。

（配置MappingJacksonHttpMessageConverter将导致你失去其他MessageConverter）

你只需要做：

public class MyObjectMapper extends ObjectMapper {

    private static final long serialVersionUID = 4219938065516862637L;

    public MyObjectMapper() {
        super();
        enable(SerializationFeature.INDENT_OUTPUT);
    }       
}

并在你的Spring配置中，创建这个bean：

@Bean 
public MyObjectMapper myObjectMapper() {        
    return new MyObjectMapper();
}

Answer 12

我正在使用 Spring 3.2.4 和 Jackson FasterXML 2.1.1。

我创建了一个自定义 JacksonObjectMapper，它使用映射对象的每个属性的显式注释：

package com.test;
import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

public class MyJaxbJacksonObjectMapper extends ObjectMapper {

public MyJaxbJacksonObjectMapper() {

    this.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY)
            .setVisibility(PropertyAccessor.CREATOR, JsonAutoDetect.Visibility.ANY)
            .setVisibility(PropertyAccessor.SETTER, JsonAutoDetect.Visibility.NONE)
            .setVisibility(PropertyAccessor.GETTER, JsonAutoDetect.Visibility.NONE)
            .setVisibility(PropertyAccessor.IS_GETTER, JsonAutoDetect.Visibility.NONE);

    this.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
    }
}

然后在上下文配置 (servlet-context.xml) 中实例化它：

<mvc:annotation-driven>
    <mvc:message-converters>

        <beans:bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
            <beans:property name="objectMapper">
                <beans:bean class="com.test.MyJaxbJacksonObjectMapper" />
            </beans:property>
        </beans:bean>

    </mvc:message-converters>
</mvc:annotation-driven>

这很好用！

Answer 13

如果您使用 Spring WebFlux，@EnableWebFlux 会覆盖任何自定义设置，例如 spring.jackson.serialization.write-dates-as-timestamps=false，因此您需要覆盖 WebFlux 的ObjectMapper 实例根据WebFlux 文档。

@Configuration
public class WebfluxConfig implements WebFluxConfigurer {
    private final ObjectMapper objectMapper;

    @Autowired
    public WebfluxConfig(ObjectMapper objectMapper) {
        this.objectMapper = objectMapper;
    }

    @Override
    public void configureHttpMessageCodecs(ServerCodecConfigurer configurer) {
        configurer.defaultCodecs().jackson2JsonEncoder(new Jackson2JsonEncoder(objectMapper));
        configurer.defaultCodecs().jackson2JsonDecoder(new Jackson2JsonDecoder(objectMapper));
    }
}