Question

我不喜欢杰克逊。

我想使用ajax但使用Google Gson。

所以我试图弄清楚如何实现我自己的HttpMessageConverter与@ResponseBody注释一起使用它。有人可以花点时间告诉我应该去的方式吗？我应该打开哪些配置？另外我想知道我是否可以这样做并仍然使用＆lt; mvc：annotation-driven /＆gt;？

提前致谢。

我已经在Spring社区Foruns问过它大约3天前没有回答所以我在这里问我是否有更好的机会。 Spring Community Forums link to my question

我也在网上进行了详尽的搜索，发现了一些关于这个主题的有趣内容，但似乎他们正考虑将它放在Spring 3.1中，我仍然使用spring 3.0.5： Jira's Spring Improvement ask

嗯......现在我正在尝试调试Spring代码以找出自己如何做到这一点，但我遇到了一些问题，比如我在这里说过： Spring Framework Build Error

如果有其他方法可以做到这一点，我想错过它，请告诉我。

Answer 1

嗯......很难找到答案，我不得不关注那些不完整信息的线索，我认为在这里发布完整答案会更好。所以下一个搜索它会更容易。

首先，我必须实现自定义HttpMessageConverter：


package net.iogui.web.spring.converter;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.nio.charset.Charset;

import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.AbstractHttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;

import com.google.gson.Gson;
import com.google.gson.JsonSyntaxException;

public class GsonHttpMessageConverter extends AbstractHttpMessageConverter<Object> {

    private Gson gson = new Gson();

    public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");

    public GsonHttpMessageConverter(){
        super(new MediaType("application", "json", DEFAULT_CHARSET));
    }

    @Override
    protected Object readInternal(Class<? extends Object> clazz,
                                  HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {

        try{
            return gson.fromJson(convertStreamToString(inputMessage.getBody()), clazz);
        }catch(JsonSyntaxException e){
            throw new HttpMessageNotReadableException("Could not read JSON: " + e.getMessage(), e);
        }

    }

    @Override
    protected boolean supports(Class<?> clazz) {
        return true;
    }

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

        //TODO: adapt this to be able to receive a list of json objects too

        String json = gson.toJson(t);

        outputMessage.getBody().write(json.getBytes());
    }

    //TODO: move this to a more appropriated utils class
    public String convertStreamToString(InputStream is) throws IOException {
        /*
         * To convert the InputStream to String we use the Reader.read(char[]
         * buffer) method. We iterate until the Reader return -1 which means
         * there's no more data to read. We use the StringWriter class to
         * produce the string.
         */
        if (is != null) {
            Writer writer = new StringWriter();

            char[] buffer = new char[1024];
            try {
                Reader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
                int n;
                while ((n = reader.read(buffer)) != -1) {
                    writer.write(buffer, 0, n);
                }
            } finally {
                is.close();
            }
            return writer.toString();
        } else {
            return "";
        }
    }

}

然后我不得不剥离annnotaion驱动的标签，并自行配置spring-mvc配置文件：


<?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/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <!-- Configures the @Controller programming model -->

    <!-- To use just with a JSR-303 provider in the classpath 
    <bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean" />
    -->

    <bean id="conversionService" class="org.springframework.format.support.FormattingConversionServiceFactoryBean" />

    <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
        <property name="webBindingInitializer">
            <bean class="net.iogui.web.spring.util.CommonWebBindingInitializer" />
        </property>
        <property name="messageConverters">
            <list>
                <bean class="org.springframework.http.converter.ByteArrayHttpMessageConverter" />
                <bean class="org.springframework.http.converter.StringHttpMessageConverter" />
                <bean class="org.springframework.http.converter.ResourceHttpMessageConverter" />
                <bean class="net.iogui.web.spring.converter.GsonHttpMessageConverter" />
                <bean class="org.springframework.http.converter.xml.SourceHttpMessageConverter" />
                <bean class="org.springframework.http.converter.xml.XmlAwareFormHttpMessageConverter" />
                <!-- bean class="org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter" /-->
            </list>
        </property>
    </bean>
    <bean id="handlerMapping" class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping" />


    <context:component-scan base-package="net.iogui.teste.web.controller"/>

    <!-- Forwards requests to the "/" resource to the "login" view -->
    <mvc:view-controller path="/" view-name="home"/>

    <!-- Handles HTTP GET requests for /resources/** by efficiently serving up static resources in the ${webappRoot}/resources/ directory -->
    <mvc:resources mapping="/resources/**" location="/resources/" />

    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
        <property name="prefix" value="/WEB-INF/view/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

</beans>

请注意，要使 Formater 和 Validator 生效，我们还必须构建自定义 webBindingInitializer ：


package net.iogui.web.spring.util;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.convert.ConversionService;
import org.springframework.validation.Validator;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.support.WebBindingInitializer;
import org.springframework.web.context.request.WebRequest;

public class CommonWebBindingInitializer implements WebBindingInitializer {

    @Autowired(required=false)
    private Validator validator;

    @Autowired
    private ConversionService conversionService;

    @Override
    public void initBinder(WebDataBinder binder, WebRequest request) {
        binder.setValidator(validator);
        binder.setConversionService(conversionService);
    }

}

有趣的是，为了使配置在没有 annotaion驱动标记的情况下工作，我们必须手动配置 AnnotationMethodHandlerAdapter 和 DefaultAnnotationHandlerMapping 。为了使 AnnotationMethodHandlerAdapter 能够处理格式和验证，我们必须配置验证器， conversionService 并构建自定义< EM>的WebBindingInitializer

我希望除了我之外，所有这些都能帮到别人。

在我绝望的搜索中，this @Bozho帖子非常有用。我也很感谢@GaryF，他的回答把我带到@Bozho post。对于那些试图在Spring 3.1中执行此操作的人，请参阅@Robby Pond回答..更容易，不是吗？

Answer 2

您需要创建一个扩展AbstractHttpMessageConverter的GsonMessageConverter，并使用m vc-message-converters标记注册您的邮件转换器。该标签将使您的转换器优先于杰克逊转换器。

Answer 3

我有一种情况，杰克逊的使用要求我改变其他组（在同一家公司）的代码。不喜欢那样。所以我选择使用Gson并根据需要注册TypeAdapters。

使用spring-test（曾经是spring-mvc-test）编写了一些转换器并编写了一些集成测试。无论我尝试了什么变化（使用mvc：annotation-driven OR手动定义bean）。他们都没有工作。这些的任何组合总是使用杰克逊转换器继续失败。

<强>答案＆GT;事实证明，MockMvcBuilders的standaloneSetup方法“硬”将消息转换器编码为默认版本，并忽略了上面的所有更改。这是有用的：

@Autowired
private RequestMappingHandlerAdapter adapter;

public void someOperation() {
  StandaloneMockMvcBuilder smmb = MockMvcBuilders.standaloneSetup(controllerToTest);
  List<HttpMessageConverter<?>> converters = adapter.getMessageConverters();
  HttpMessageConverter<?> ary[] = new HttpMessageConverter[converters.size()];
  smmb.setMessageConverters(conveters.toArray(ary));
  mockMvc = smmb.build();
   .
   .
}

希望这有助于某人，最后我使用注释驱动和重新设计android的转换器

Answer 4

如果你想在不弄乱xml的情况下添加消息转换器，这是一个简单的例子

@Autowired
private RequestMappingHandlerAdapter adapter;

@PostConstruct
public void initStuff() {
    List<HttpMessageConverter<?>> messageConverters = adapter.getMessageConverters();
    BufferedImageHttpMessageConverter imageConverter = new BufferedImageHttpMessageConverter();;
    messageConverters.add(0,imageConverter);
}

Answer 5

Robby Pond基本上是正确的，但请注意他建议使用mvc：message-converters标签要求你使用3.1。由于3.1目前只是一个里程碑版本（M1），我建议在创建后以这种方式注册转换器：

<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    <property name="messageConverters">
      <util:list id="beanList">
        <ref bean="someMessageConverter"/>
        <ref bean="someOtherMessageConverter"/>
      </util:list>
    </property>
</bean>

Answer 6

或者如Jira's Spring Improvement ask中所述，编写一个将HttpMessageConvertor添加到AnnotationMethodHandlerAdapter

的BeanPostProcessor

Answer 7

请注意，GsonHttpMessageConverter最近添加到Spring（4.1）

Answer 8

您可以通过将WebConfig文件编写为Java文件来完成此操作。使用WebMvcConfigurerAdapter扩展配置文件并覆盖extendMessageConverters方法以添加您想要的消息转换器。此方法将保留Spring添加的默认转换器，并在最后添加转换器。显然，您可以完全控制列表，并且可以在列表中添加所需的位置。

@Configuration
@EnableWebMvc
@ComponentScan(basePackageClasses={WebConfig.class})
public class WebConfig extends WebMvcConfigurerAdapter {
    @Override
    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
      converters.add(new GsonHttpMessageConverter());
   }
}

package net.iogui.web.spring.converter;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.nio.charset.Charset;

import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.AbstractHttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;

import com.google.gson.Gson;
import com.google.gson.JsonSyntaxException;

public class GsonHttpMessageConverter extends AbstractHttpMessageConverter<Object> {

private Gson gson = new Gson();

public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");

public GsonHttpMessageConverter(){
    super(new MediaType("application", "json", DEFAULT_CHARSET));
}

@Override
protected Object readInternal(Class<? extends Object> clazz,
                              HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {

    try{
        return gson.fromJson(convertStreamToString(inputMessage.getBody()), clazz);
    }catch(JsonSyntaxException e){
        throw new HttpMessageNotReadableException("Could not read JSON: " + e.getMessage(), e);
    }

}

@Override
protected boolean supports(Class<?> clazz) {
    return true;
}

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

    //TODO: adapt this to be able to receive a list of json objects too

    String json = gson.toJson(t);

    outputMessage.getBody().write(json.getBytes());
}

//TODO: move this to a more appropriated utils class
public String convertStreamToString(InputStream is) throws IOException {
    /*
     * To convert the InputStream to String we use the Reader.read(char[]
     * buffer) method. We iterate until the Reader return -1 which means
     * there's no more data to read. We use the StringWriter class to
     * produce the string.
     */
    if (is != null) {
        Writer writer = new StringWriter();

        char[] buffer = new char[1024];
        try {
            Reader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
            int n;
            while ((n = reader.read(buffer)) != -1) {
                writer.write(buffer, 0, n);
            }
        } finally {
            is.close();
        }
        return writer.toString();
    } else {
        return "";
    }
}

使用@ResponseBody定制HttpMessageConverter来做Json的事情

8 个答案: