Spring @RestController响应Content-Type修改：Filter设置不生效问题

我尝试在Filter类中修改HttpServletResponse的Content-Type，但修改未生效。响应的Content-Type仍为application/json，预期应为application/xml。

现有代码 #

Filter类代码 #

@Component
@Order(1)
public class TestFilter implements javax.servlet.Filter {
    @Override
    public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)
            throws IOException, ServletException {
        if (arg1 instanceof HttpServletResponse) {
            HttpServletResponse httpServletResponse = (HttpServletResponse) arg1;
            httpServletResponse.setContentType("application/xml");
            arg1.setContentType("application/xml");
            
            String contentType = httpServletResponse.getContentType();  
            System.out.println("contentType : "+contentType);
            
            arg2.doFilter(arg0, new HttpServletResponseWrapper(httpServletResponse) {
                @Override
                public void setContentType(final String type) {
                    
                }
            });
            String contentType1 = httpServletResponse.getContentType();
            System.out.println("contentType1 : "+contentType1);
            String contentType2 = httpServletResponse.getContentType();
            System.out.println("contentType2 : "+contentType2);
        }
    }
}

Controller类代码 #

@RestController
public class TestController {
    
    @PostMapping(path="/test", consumes = MediaType.ALL_VALUE,  
            produces = { MediaType.APPLICATION_JSON_VALUE, MediaType.APPLICATION_XML_VALUE })
    public String test() {
        return "<SUCCESS></SUCCESS>";
    }
}

响应日志 #

contentType : application/xml
contentType1 : application/json
contentType2 : application/json

问题分析 #

1. 现有HttpServletResponseWrapper仅重写了setContentType但为空实现，Spring MVC内部可能直接操作原始响应对象的Header设置Content-Type，导致拦截失效。
2. Controller的produces声明了两种响应类型，Spring MVC会优先根据请求的Accept头选择；若请求未指定Accept，默认会选用数组第一个类型application/json，覆盖Filter中设置的值。

修复方案 #

方案一：增强Filter的拦截逻辑 #

修改Filter，同时拦截setContentType和setHeader方法，强制将Content-Type设置为目标值，并且在请求处理完成后再次确认设置：

@Component
@Order(1)
public class TestFilter implements javax.servlet.Filter {
    @Override
    public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)
            throws IOException, ServletException {
        if (arg1 instanceof HttpServletResponse) {
            HttpServletResponse httpServletResponse = (HttpServletResponse) arg1;
            final String targetContentType = "application/xml";
            
            // 初始化设置
            httpServletResponse.setContentType(targetContentType);
            System.out.println("contentType : " + httpServletResponse.getContentType());
            
            // 包装响应，拦截所有修改Content-Type的操作
            HttpServletResponseWrapper responseWrapper = new HttpServletResponseWrapper(httpServletResponse) {
                @Override
                public void setContentType(String type) {
                    // 强制使用目标类型
                    super.setContentType(targetContentType);
                }

                @Override
                public void setHeader(String name, String value) {
                    if ("Content-Type".equalsIgnoreCase(name)) {
                        super.setHeader(name, targetContentType);
                    } else {
                        super.setHeader(name, value);
                    }
                }
            };
            
            // 继续执行请求链
            arg2.doFilter(arg0, responseWrapper);
            
            // 最后再确认设置一次，防止遗漏
            httpServletResponse.setContentType(targetContentType);
            System.out.println("contentType after doFilter: " + httpServletResponse.getContentType());
        }
    }
}

方案二：直接修改Controller的produces #

如果不需要动态切换响应类型，直接将Controller的produces指定为唯一的application/xml，Spring MVC会直接返回该类型：

@RestController
public class TestController {
    
    @PostMapping(path="/test", consumes = MediaType.ALL_VALUE,  
            produces = MediaType.APPLICATION_XML_VALUE)
    public String test() {
        return "<SUCCESS></SUCCESS>";
    }
}

注意事项 #

• 若请求的Accept头明确指定了application/json，方案一的Filter会强制覆盖为application/xml，而方案二会直接返回application/xml，忽略Accept头。
• Filter的@Order(1)确保它在其他Filter之前执行，避免被后续Filter覆盖设置。

内容的提问来源于stack exchange，提问作者ASP