Java 如何在 Spring MVC REST 中为 JSON 设置内容长度？
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How to set content-length in Spring MVC REST for JSON?
提问by ruslanys
I have some code:
我有一些代码：
@RequestMapping(value = "/products/get", method = RequestMethod.GET)
public @ResponseBody List<Product> getProducts(@RequestParam(required = true, value = "category_id") Long categoryId) {
// some code here
return new ArrayList<>();
}
How could I configure Spring MVC (or MappingHymanson2HttpMessageConverter.class) to set right header Content-Length by default? Because now my response header content-lengthequal to -1.
默认情况下，如何配置 Spring MVC（或 MappingHymanson2HttpMessageConverter.class）以设置正确的标头 Content-Length？因为现在我的响应头content-length等于 -1。
回答by Woody Sun
You can add ShallowEtagHeaderFilter to filter chain. The following snippet works for me.
您可以添加 ShallowEtagHeaderFilter 来过滤链。以下代码段对我有用。
import java.util.Arrays;
import org.springframework.boot.context.embedded.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.filter.ShallowEtagHeaderFilter;
@Configuration
public class FilterConfig {
@Bean
public FilterRegistrationBean filterRegistrationBean() {
FilterRegistrationBean filterBean = new FilterRegistrationBean();
filterBean.setFilter(new ShallowEtagHeaderFilter());
filterBean.setUrlPatterns(Arrays.asList("*"));
return filterBean;
}
}
The response body will looks like the below:
响应正文如下所示：
HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
X-Application-Context: application:sxp:8090
ETag: "05e7d49208ba5db71c04d5c926f91f382"
Content-Type: application/json;charset=UTF-8
Content-Length: 232
Date: Wed, 16 Dec 2015 06:53:09 GMT
回答by Dmitry Buzoverya
The following filter in chain sets content-length:
链中的以下过滤器设置内容长度：
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.util.ContentCachingResponseWrapper;
public class MyFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
ContentCachingResponseWrapper responseWrapper = new ContentCachingResponseWrapper((HttpServletResponse) response);
chain.doFilter(request, responseWrapper);
responseWrapper.copyBodyToResponse();
}
@Override
public void destroy() {
}
}
The main idea that all content is cached in ContentCachingResponseWrapper and finally content-length is set when you call copyBodyToResponse().
主要思想是所有内容都缓存在 ContentCachingResponseWrapper 中，最后在调用 copyBodyToResponse() 时设置 content-length。
