json - 使用 @ResponseBody 自定义 HttpMessageConverter 来做 Json 事情

Question

我不喜欢 jackson 。

我想使用 ajax，但要使用 Google Gson。

所以我试图弄清楚如何实现我自己的 HttpMessageConverter 以将其与 @ResponseBody 注释一起使用。有人可以花点时间告诉我我应该走的路吗？我应该打开哪些配置？另外我想知道我是否可以这样做并且仍然使用 ？

提前致谢。

大约 3 天前，我已经在 Spring Community Foruns 中询问过，但没有得到答复，所以我在这里询问是否有更好的机会。 Spring Community Forums link to my question

我还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，但似乎他们正在考虑将其放在 Spring 3.1 中，而我仍在使用 spring 3.0.5: Jira's Spring Improvement ask

嗯...现在我正在尝试调试 Spring 代码以了解自己如何做到这一点，但我遇到了一些问题，就像我在这里所说的那样: Spring Framework Build Error

如果有其他方法可以做到这一点而我错过了，请告诉我。

Answer 1

嗯...很难找到答案，我必须遵循很多线索来获取不完整的信息，所以我认为在这里发布完整的答案会很好。所以下一个搜索这个会更容易。

首先我必须实现自定义的 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 "";
        }
    }

}

然后我只好去掉annnotaion-driven标签，在spring-mvc配置文件上全部手动配置:

<?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>

看到，为了使 Formater 和 Validator 工作，我们也必须构建一个自定义的 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-driven 标签的情况下工作，我们必须手动配置一个 AnnotationMethodHandlerAdapter 和一个 DefaultAnnotationHandlerMapping。为了使 AnnotationMethodHandlerAdapter 能够处理格式化和验证，我们必须配置一个 validator、一个 conversionService 并构建一个自定义 em>webBindingInitializer.

我希望这一切对我以外的其他人有所帮助。

在我绝望的搜索中，this @Bozho 帖子非常有用。我也很感谢@GaryF，因为他的回答把我带到了@Bozho post。 .对于尝试在 Spring 3.1 中执行此操作的您，请参阅@Robby Pond 的答案。要容易得多，不是吗？