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java – Spring REST | MappingJacksonHttpMessageConverter生成无效的JSON（springmvc输出json）

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在本文中，我们将带你了解java–SpringREST|MappingJacksonHttpMessageConverter生成无效的JSON在这篇文章中，我们将为您详细介绍java–SpringRE

在本文中，我们将带你了解java – Spring REST | MappingJacksonHttpMessageConverter生成无效的JSON在这篇文章中，我们将为您详细介绍java – Spring REST | MappingJacksonHttpMessageConverter生成无效的JSON的方方面面，并解答springmvc输出json常见的疑惑，同时我们还将给您一些技巧，以帮助您实现更有效的Fastjson、Jackson 与 SpringMVC 整合的 MessageConverter 配置、java – 自定义的Jackson HttpMessageConverter不再适用于Spring 4.2、java.lang.ClassNotFoundException：org.springframework.http.converter.json.MappingJackson2HttpMessageConverter、MappingJackson2HttpMessageConverter 如何处理 Decimal 小数点保留 2 位问题？。

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java – Spring REST | MappingJacksonHttpMessageConverter生成无效的JSON（springmvc输出json）

java – Spring REST | MappingJacksonHttpMessageConverter生成无效的JSON（springmvc输出json）

我用Spring实现了一个RESTful Web服务.该服务基于Accept标头以XML或JSON响应.这是context.xml映射：

这是我的控制器方法：

@Controller
@RequestMapping(value = "/entityService")
class RestfulEntityService {

  @Resource
  private EntityService entityService;

  @ResponseBody
  @RequestMapping(value = "/getAllEntities",method = RequestMethod.GET)
  public List

XML响应是有效的,但是,当客户端将Accept标头设置为application / json时,响应是无效的JSON.

这是JSON响应示例：

[{"id":3,"attributes":[{"id":18,"attributeValue":null,"attributeName":"mobile","attributeType":"varchar(40)","entity":{"id":3,"attributes": ..... repeats for a while and then stops..
最佳答案
您使用XStream序列化XML响应,使用Jackson JSON序列化JSON响应.查看您发布的JSON输出,似乎有一个循环引用问题.我猜测实体有一个属性列表,每个属性都指向它们各自的实体. XStream通过使用XPath透明地处理循环引用,这允许在反序列化返回到对象时保留引用.从v1.6开始,Jackson能够处理循环引用,但是你需要通过@JsonManagedReference和@JsonBackReference来注释你的序列化实体来帮助它.我认为杰克逊在允许JSON序列化中的返回引用方面是独一无二的.

请参阅handling bi-directional references using declarative methods的杰克逊文档以供参考.

Fastjson、Jackson 与 SpringMVC 整合的 MessageConverter 配置

Fastjson、Jackson 与 SpringMVC 整合的 MessageConverter 配置

1.Jackson

maven 依赖

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.7.1</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-xml</artifactId>
    <version>2.7.1</version>
</dependency>

springmvc-servlet.xml 中配置

<mvc:annotation-driven>
    <mvc:message-converters>
        <bean class="org.springframework.http.converter.StringHttpMessageConverter">
            <constructor-arg value="UTF-8"/>
        </bean>
    </mvc:message-converters>
</mvc:annotation-driven>

2.FastJson

由于 FastJson 针对 Spring4.2 以后进行特殊优化，具体如图

所以 FastJson 可以分为 Spring4.2 及以下配置和 Spring4.2 以上的不同配置

2.1Spring4.2 及以下配置

maven 依赖

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.7</version>
</dependency>

springmvc-servlet.xml 中配置

<mvc:annotation-driven>
        <mvc:message-converters register-defaults="true">
            <bean class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter">
                <property name="supportedMediaTypes">
                    <list>
                        <value>text/html;charset=UTF-8</value>
                        <value>application/json</value>
                        <value>application/xml;charset=UTF-8</value>
                    </list>
                </property>
                <property name="features">
                    <list>
                        <value>WriteMapNullValue</value>
                        <value>QuoteFieldNames</value>
                        <value>WriteDateUseDateFormat</value>
                    </list>
                </property>
            </bean>
        </mvc:message-converters>
</mvc:annotation-driven>

2.2Spring4.2 以上配置

maven 依赖

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.7</version>
</dependency>

springmvc-servlet.xml 中配置

<mvc:annotation-driven validator="validator">
        <mvc:message-converters register-defaults="true">
            <ref bean="stringHttpMessageConverter"/>
            <ref bean="fastJsonHttpMessageConverter"/>
        </mvc:message-converters>
</mvc:annotation-driven>
<!--FastJson(spring4.2x版本以上)-->
<bean id="stringHttpMessageConverter"
          class="org.springframework.http.converter.StringHttpMessageConverter">
        <constructor-arg value="UTF-8" index="0"></constructor-arg>
        <property name="supportedMediaTypes">
            <list>
                <value>text/plain;charset=UTF-8</value>
            </list>
        </property>
</bean>

<bean id="fastJsonHttpMessageConverter" class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter4">
        <property name="supportedMediaTypes">
            <list>
                <value>text/html;charset=UTF-8</value>
                <value>application/json;charset=UTF-8</value>
            </list>
        </property>
        <property name="fastJsonConfig">
            <bean class="com.alibaba.fastjson.support.config.FastJsonConfig">
                <property name="features">
                    <list>
                        <value>AllowArbitraryCommas</value>
                        <value>AllowUnQuotedFieldNames</value>
                        <value>DisableCircularReferenceDetect</value>
                    </list>
                </property>
                <property name="dateFormat" value="yyyy-MM-dd HH:mm:ss"></property>
            </bean>
        </property>
</bean>

java – 自定义的Jackson HttpMessageConverter不再适用于Spring 4.2

java – 自定义的Jackson HttpMessageConverter不再适用于Spring 4.2

我正在从 Spring Platform版本1.1.3.RELEASE更新应用程序到2.0.1.RELEASE,这将Spring Framework版本从4.1.7更改为4.2.4,而Jackson从2.4.6到2.6.4.在Spring或Jackson处理自定义HttpMessageConverter实现方面似乎没有任何重大变化,但是我的自定义 JSON序列化未能发生,我无法确定为什么.在以前的Spring Platform版本中,以下工作正常：

模型

@JsonFilter("fieldFilter")
public class MyModel { 
    /*model fields and methods*/ 
}

模型包装

public class ResponseEnvelope {

    private Set<String> fieldSet;
    private Set<String> exclude;
    private Object entity;

    public ResponseEnvelope(Object entity) {
        this.entity = entity;
    }

    public ResponseEnvelope(Object entity,Set<String> fieldSet,Set<String> exclude) {
        this.fieldSet = fieldSet;
        this.exclude = exclude;
        this.entity = entity;
    }

    public Object getEntity() {
        return entity;
    }

    @JsonIgnore
    public Set<String> getFieldSet() {
        return fieldSet;
    }

    @JsonIgnore
    public Set<String> getExclude() {
        return exclude;
    }

    public void setExclude(Set<String> exclude) {
        this.exclude = exclude;
    }

    public void setFieldSet(Set<String> fieldSet) {
        this.fieldSet = fieldSet;
    }

    public void setFields(String fields) {
        Set<String> fieldSet = new HashSet<String>();
        if (fields != null) {
            for (String field : fields.split(",")) {
                fieldSet.add(field);
            }
        }
        this.fieldSet = fieldSet;
    }
}

调节器

@Controller
public class MyModelController {

    @Autowired MyModelRepository myModelRepository;

    @RequestMapping(value = "/model",method = RequestMethod.GET,produces = { MediaType.APPLICATION_JSON_VALUE })
    public httpentity find(@RequestParam(required=false) Set<String> fields,@RequestParam(required=false) Set<String> exclude){
        List<MyModel> objects = myModelRepository.findAll();
        ResponseEnvelope envelope = new ResponseEnvelope(objects,fields,exclude);
        return new ResponseEntity<>(envelope,HttpStatus.OK);
    }
}

自定义HttpMessageConverter

public class FilteringJackson2HttpMessageConverter extends MappingJackson2HttpMessageConverter {

    private boolean prefixJson = false;

    @Override
    public void setPrefixJson(boolean prefixJson) {
        this.prefixJson = prefixJson;
        super.setPrefixJson(prefixJson);
    }

    @Override
    protected void writeInternal(Object object,HttpOutputMessage outputMessage)
            throws IOException,HttpMessageNotWritableException {

        ObjectMapper objectMapper = getobjectMapper();
        JsonGenerator jsonGenerator = objectMapper.getFactory().createGenerator(outputMessage.getBody());

        try {

            if (this.prefixJson) {
                jsonGenerator.writeraw(")]}',");
            }

            if (object instanceof ResponseEnvelope) {

                ResponseEnvelope envelope = (ResponseEnvelope) object;
                Object entity = envelope.getEntity();
                Set<String> fieldSet = envelope.getFieldSet();
                Set<String> exclude = envelope.getExclude();
                FilterProvider filters = null;

                if (fieldSet != null && !fieldSet.isEmpty()) {
                    filters = new SimpleFilterProvider()
                            .addFilter("fieldFilter",SimpleBeanPropertyFilter.filterOutAllExcept(fieldSet))
                                .setFailOnUnkNownId(false);
                } else if (exclude != null && !exclude.isEmpty()) {
                    filters = new SimpleFilterProvider()
                            .addFilter("fieldFilter",SimpleBeanPropertyFilter.serializeAllExcept(exclude))
                                .setFailOnUnkNownId(false);
                } else {
                    filters = new SimpleFilterProvider()
                            .addFilter("fieldFilter",SimpleBeanPropertyFilter.serializeAllExcept())
                                .setFailOnUnkNownId(false);
                }

                objectMapper.setFilterProvider(filters);
                objectMapper.writeValue(jsonGenerator,entity);

            } else if (object == null){
                jsonGenerator.writeNull();
            } else {
                FilterProvider filters = new SimpleFilterProvider().setFailOnUnkNownId(false);
                objectMapper.setFilterProvider(filters);
                objectMapper.writeValue(jsonGenerator,object);
            }

        } catch (JsonProcessingException e){
            e.printstacktrace();
            throw new HttpMessageNotWritableException("Could not write JSON: " + e.getMessage());
        }

    }
}

组态

@Configuration
@EnableWebMvc
public class WebServicesConfig extends WebMvcConfigurerAdapter {

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        FilteringJackson2HttpMessageConverter jsonConverter = new FilteringJackson2HttpMessageConverter();
        jsonConverter.setSupportedMediaTypes(MediaTypes.APPLICATION_JSON);
        converters.add(jsonConverter);
    }

    // Other configurations
}

现在我得到这个异常(被Spring记录下来),并且在进行任何请求时有一个500错误：

[main] WARN  o.s.w.s.m.s.DefaultHandlerExceptionResolver - Failed to write HTTP message: 
  org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: 
  Can not resolve PropertyFilter with id 'fieldFilter'; 
  no FilterProvider configured (through reference chain:
  org.oncoblocks.centromere.web.controller.ResponseEnvelope["entity"]->java.util.ArrayList[0]); 
  nested exception is com.fasterxml.jackson.databind.JsonMappingException: 
  Can not resolve PropertyFilter with id 'fieldFilter'; 
  no FilterProvider configured (through reference chain: 
  org.oncoblocks.centromere.web.controller.ResponseEnvelope["entity"]->java.util.ArrayList[0])

configureMessageConverters方法执行,但它看起来不像在请求期间自定义转换器被使用.另一个消息转换器可能会阻止这个消息转发到达我的响应？我的理解是,覆盖configureMessageConverters会阻止除了手动注册的转换器之外的转换器.

除了通过Spring平台更新依赖关系,这个代码的工作版本和非工作版本之间都没有改变. JSON序列化有什么变化,我刚刚在文档中丢失了吗？

编辑

进一步测试产生奇怪的结果.我想测试检查以下事情：

我的自定义HttpMessageConverter是否正在注册？
>另一个转换器是否覆盖/取代它？
>这是我的测试设置问题吗？

所以,我添加了一个额外的测试,并看看输出：

@Autowired WebApplicationContext webApplicationContext;

@Before
public void setup(){
    mockmvc = mockmvcBuilders.webAppContextSetup(webApplicationContext).build();
}

@Test
public void test() throws Exception {
    RequestMappingHandlerAdapter adapter = (RequestMappingHandlerAdapter) webApplicationContext.getBean("requestMappingHandlerAdapter");
    List<EntrezGene> genes = EntrezGene.createDummyData();
    Set<String> exclude = new HashSet<>();
    exclude.add("entrezGeneId");
    ResponseEnvelope envelope = new ResponseEnvelope(genes,new HashSet<String>(),exclude);
    for (HttpMessageConverter converter: adapter.getMessageConverters()){
        System.out.println(converter.getClass().getName());
        if (converter.canWrite(ResponseEnvelope.class,MediaType.APPLICATION_JSON)){
            MockHttpOutputMessage message =  new MockHttpOutputMessage();
            converter.write((Object) envelope,MediaType.APPLICATION_JSON,message);    
            System.out.println(message.getBodyAsstring());
        }
    }
}

…它工作正常.我的信封对象及其内容被序列化并被正确过滤.因此,在到达消息转换器之前,请求处理有问题,或者mockmvc如何测试请求发生了变化.

解决方法

你的配置没问题没有从您的自定义转换器调用writeInternal()的原因是因为您覆盖了错误的方法.

看看4.2.4.RELEASE的源代码

AbstractMessageConverterMethodProcessor#writeWithMessageConverters

protected <T> void writeWithMessageConverters(T returnValue,MethodParameter returnType,ServletServerHttpRequest inputMessage,ServletServerHttpResponse outputMessage)
            throws IOException,HttpMediaTypeNotAcceptableException,HttpMessageNotWritableException {
    ...
    ((GenericHttpMessageConverter<T>) messageConverter).write(returnValue,returnValueType,selectedMediaType,outputMessage);
    ...
}

AbstractGenericHttpMessageConverter#写

public final void write(final T t,final Type type,MediaType contentType,HttpMessageNotWritableException {
    ...
    writeInternal(t,type,outputMessage);
    ...
}

从AbstractGenericHttpMessageConverter#write(…)中调用的writeInternal(…)方法有三个参数 – (T t,Type type,HttpOutputMessage outputMessage).您将覆盖只有2个参数的writeInternal(…)的重载版本(T t,HttpOutputMessage outputMessage).

但是,在版本4.1.7.RELEASE中,情况并非如此,因此是您问题的根本原因.在这个版本中使用的writeInternal(…)是另一个重载的方法(有2个参数的方法),你已经被覆盖了.这解释了为什么它在4.1.7.RELEASE中正常工作.

@Override
public final void write(final T t,outputMessage);
    ...
}

所以,为了解决你的问题,而不是覆盖writeInternal(Object对象,HttpOutputMessage outputMessage),重写writeInternal(Object对象,Type类型,HttpOutputMessage outputMessage)

java.lang.ClassNotFoundException：org.springframework.http.converter.json.MappingJackson2HttpMessageConverter

java.lang.ClassNotFoundException：org.springframework.http.converter.json.MappingJackson2HttpMessageConverter

我在项目中使用spring-integration。在码头容器中部署应用程序时，出现以下异常：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'integrationRequestMappingHandlerMapping': Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'inboundhttpJobRequestGateway': Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.integration.http.inbound.HttpRequestHandlingMessagingGateway]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/springframework/http/converter/json/MappingJackson2HttpMessageConverter
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:527)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:585)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:913)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:464)
    at com.dsths.spring.web.DsthsContextLoaderListener.configureAndRefreshWebApplicationContext(DsthsContextLoaderListener.java:97)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:284)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:111)
    at org.eclipse.jetty.server.handler.ContextHandler.callContextInitialized(ContextHandler.java:771)
    at org.eclipse.jetty.servlet.ServletContextHandler.callContextInitialized(ServletContextHandler.java:411)
    at org.eclipse.jetty.server.handler.ContextHandler.startContext(ContextHandler.java:763)
    at org.eclipse.jetty.servlet.ServletContextHandler.startContext(ServletContextHandler.java:247)
    at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1238)
    at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:706)
    at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:480)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:64)
    at com.dsths.common.container.core.deploy.DeploymentManager.deploy(DeploymentManager.java:54)
    at com.dsths.common.container.core.deploy.DeploymentManager$$FastClassByCGLIB$$f5bc43eb.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:698)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
    at org.springframework.aop.interceptor.AsyncExecutionInterceptor$1.call(AsyncExecutionInterceptor.java:95)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:724)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'inboundhttpJobRequestGateway': Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.integration.http.inbound.HttpRequestHandlingMessagingGateway]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/springframework/http/converter/json/MappingJackson2HttpMessageConverter
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:288)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1035)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:939)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:485)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1093)
    at org.springframework.integration.http.inbound.IntegrationRequestMappingHandlerMapping.detectHandlerMethods(IntegrationRequestMappingHandlerMapping.java:103)
    at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.initHandlerMethods(AbstractHandlerMethodMapping.java:109)
    at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.initApplicationContext(AbstractHandlerMethodMapping.java:89)
    at org.springframework.context.support.ApplicationObjectSupport.initApplicationContext(ApplicationObjectSupport.java:119)
    at org.springframework.web.context.support.WebApplicationObjectSupport.initApplicationContext(WebApplicationObjectSupport.java:72)
    at org.springframework.context.support.ApplicationObjectSupport.setApplicationContext(ApplicationObjectSupport.java:73)
    at org.springframework.context.support.ApplicationContextAwareProcessor.invokeAwareInterfaces(ApplicationContextAwareProcessor.java:117)
    at org.springframework.context.support.ApplicationContextAwareProcessor.postProcessBeforeInitialization(ApplicationContextAwareProcessor.java:92)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:394)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1448)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
    ... 29 more
Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.integration.http.inbound.HttpRequestHandlingMessagingGateway]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/springframework/http/converter/json/MappingJackson2HttpMessageConverter
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:162)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:110)
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:280)
    ... 49 more
Caused by: java.lang.NoClassDefFoundError: org/springframework/http/converter/json/MappingJackson2HttpMessageConverter
    at org.springframework.integration.http.inbound.HttpRequestHandlingEndpointSupport.<init>(HttpRequestHandlingEndpointSupport.java:166)
    at org.springframework.integration.http.inbound.HttpRequestHandlingMessagingGateway.<init>(HttpRequestHandlingMessagingGateway.java:72)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:147)
    ... 51 more
Caused by: java.lang.ClassNotFoundException: org.springframework.http.converter.json.MappingJackson2HttpMessageConverter
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at com.dsths.common.container.ContainerClassLoader.loadClass(ContainerClassLoader.java:136)
    at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:429)
    at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:382)
    ... 58 more

我有两个罐子jackson-core-asl-1.8.3，并jackson-core-2.3.1在类路径中。仍然我得到错误。如何解决问题？

MappingJackson2HttpMessageConverter 如何处理 Decimal 小数点保留 2 位问题？

MappingJackson2HttpMessageConverter 如何处理 Decimal 小数点保留 2 位问题？

这样使用不行，为什么？

public class CustomObjectMapper extends JsonSerializer<BigDecimal> {



@Override
public void serialize(BigDecimal value, JsonGenerator gen, SerializerProvider serializers)
throws IOException, JsonProcessingException {
DecimalFormat df = new DecimalFormat ("#.00");// 四舍五入
gen.writeString(df.format(value));

}  

}



<mvc:annotation-driven>
<mvc:message-converters>
<bean
>
<property name="objectMapper">
     <bean/>
<!-- <bean> -->
<!-- <property name="decimalFormat"> -->
<!-- <bean> -->
<!-- <constructor-arg type="java.lang.String" value="#.00" /> -->
<!-- </bean> -->
<!-- </property> -->
<!-- </bean> -->
</property>
</bean>
</mvc:message-converters>
</mvc:annotation-driven>

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