【SSM分布式架构电商项目-13】统一支持jsonp

扩展CallbackMappingJackson2HttpMessageConverter

以后如果很多方法都需要jsonp的支持，那么下面这种写法就会使得我们的代码特别繁琐：

我们可以自己写一个自定义的消息转化器，继承MappingJackson2HttpMessageConverter：

package com.taotao.common.spring.exetend.converter.json;

import java.io.IOException;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.StringUtils;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonProcessingException;

public class CallbackMappingJackson2HttpMessageConverter extends MappingJackson2HttpMessageConverter {

    // 做jsonp的支持的标识，在请求参数中加该参数
    private String callbackName;

    @Override
    protected void writeInternal(Object object, HttpOutputMessage outputMessage) throws IOException,
            HttpMessageNotWritableException {
        // 从threadLocal中获取当前的Request对象
        HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder
                .currentRequestAttributes()).getRequest();
        String callbackParam = request.getParameter(callbackName);
        if (StringUtils.isEmpty(callbackParam)) {
            // 没有找到callback参数，直接返回json数据
            super.writeInternal(object, outputMessage);
        } else {
            JsonEncoding encoding = getJsonEncoding(outputMessage.getHeaders().getContentType());
            try {
                String result = callbackParam + "(" + super.getObjectMapper().writeValueAsString(object)
                        + ");";
                IOUtils.write(result, outputMessage.getBody(), encoding.getJavaName());
            } catch (JsonProcessingException ex) {
                throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
            }
        }

    }

    public String getCallbackName() {
        return callbackName;
    }

    public void setCallbackName(String callbackName) {
        this.callbackName = callbackName;
    }

}

然后在common中还需要导入依赖：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <parent>
        <groupId>com.taotao.parent</groupId>
        <artifactId>taotao-parent</artifactId>
        <version>0.0.1-SNAPSHOT</version>
  </parent>
  <groupId>com.taotao-common</groupId>
  <artifactId>taotao-common</artifactId>
  <dependencies>
     <!-- Jackson Json处理工具包 -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <scope>provided</scope>
        </dependency>
        <!-- Apache工具组件 -->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-io</artifactId>
        </dependency>
        <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
            <version>2.6.0</version>
        </dependency>
        <!-- httpclient -->
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
        </dependency>
  </dependencies>
</project>

配置

Controller实现

现在返回ResponseEntity<ItemCatResult>就不存在乱码问题，因为不会走StringHttpMessageConverter，而会走继承了MappingJackson2HttpMessageConverter的自定义CallbackMappingJackson2HttpMessageConverter

测试：