JSONP与Spring 3.0和Jackson

Question

使用Spring 3.0返回JSON响应足以@ResponseBody在@RequestMapping内部添加注释a @Controller.如果加载了MapppingJacksonJson库并且客户端发送了Accept标头application/json,则它将起作用.

JSONP怎么样？是否可以退货以及如何退货？

Answer 1

这篇博文显示了一个正确而紧凑的解决方案:在Spring MVC 3.0.x中实现JSONP

这个适用于Spring 3.1:Spring 3.1中的XML,JSON,JSON-P Web服务端点

对于Spring 3.2,这是一个基于Jackson2的JSONP转换器:

import java.io.IOException;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;

public class MappingJackson2JsonpHttpMessageConverter
    extends MappingJackson2HttpMessageConverter {

    @Override
    protected void writeInternal(Object object, HttpOutputMessage outputMessage)
        throws IOException, HttpMessageNotWritableException {
        JsonEncoding encoding = getJsonEncoding(outputMessage.getHeaders().getContentType());
        JsonGenerator jsonGenerator = this.getObjectMapper().getFactory().createJsonGenerator(outputMessage.getBody(), encoding);        

        try {
            String jsonPadding = "callback";            

            // If the callback doesn't provide, use the default callback
            if (object instanceof IJsonpObject) {
                String jsonCallback = ((IJsonpObject)object).getJsonCallback();
                if (jsonCallback != null) {
                    jsonPadding = jsonCallback;
                }
            }            

            jsonGenerator.writeRaw(jsonPadding);
            jsonGenerator.writeRaw('(');
            this.getObjectMapper().writeValue(jsonGenerator, object);
            jsonGenerator.writeRaw(");");
            jsonGenerator.flush();
        } catch (JsonProcessingException ex) {
            throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
        }
    }
}

要添加它,请将此bean放在您的配置中:

import java.util.List;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.ContentNegotiationConfigurer;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import com.google.common.collect.Lists;

public class MyWebMvcConfigurer extends WebMvcConfigurerAdapter {

    @Override
    public void configureMessageConverters( List<HttpMessageConverter<?>> converters ) {
        MappingJackson2JsonpHttpMessageConverter converter = new MappingJackson2JsonpHttpMessageConverter();

        converter.setSupportedMediaTypes( Lists.newArrayList(
            new MediaType( "application", "x-javascript" ),
            new MediaType( "application", "javascript" ),
            new MediaType( "text", "javascript" )
        ) );

        converters.add( converter );
    }

}

Answer 2

既然Spring 4.1你可以这样轻松地做到这一点:

@RestController
public class MyController {
    @RequestMapping("/endpoint")
    MappingJacksonValue getData(@RequestParam String callback) {
        MappingJacksonValue value = new MappingJacksonValue(new MyPojo());
        value.setJsonpFunction(callback);
        return value;
    }
}