content: package com.taotao.common.spring.extend.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;
  	}
  
  }
  