如何在springmvc 中返回jsonp格式

傷城~ 2022-05-25 21:20 175阅读 0赞

在这里需要使用springmvc4.1或之上的版本。  
需要继承MappingJackson2HttpMessageConverter这个类，重写writeInternal方法。  
基本步骤：  
1写继承MappingJackson2HttpMessageConverter的类

package com.ljlx.filter;
    
    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;
    //springmvc支持jsonp返回
    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; 
        }  
    }

2在springmvc.xml文件中添加上自定义消息转换器

<mvc:annotation-driven >
           
        <mvc:message-converters>  
              
            <bean class="com.ljlx.filter.CallbackMappingJackson2HttpMessageConverter">  
                  
                <property name="callbackName" value="callback"></property>  
            </bean>  
        </mvc:message-converters>
        </mvc:annotation-driven>