仅在Java Filter中更改ContentType或CharacterEncoding如果ContentType =

我正在尝试确保来自基于Jersey的 java应用程序的所有 JSON响应都在其ContentType标头中附加了UTF-8字符编码参数.

因此,如果它是JSON响应,我想要Content-Type的响应头

Content-Type: application/json;charset=UTF-8

编辑：我知道我可以根据具体情况这样做,但我想全局地这样做,因此它会影响内容类型为“application / json”的所有内容响应.

如果我只是尝试在我的过滤器中设置字符编码,无论内容类型如何,它都可以正常工作.但是我只想在ContentType为“application / json”时设置字符编码.我发现response.getContentType()方法总是返回null,除非我先调用chain.doFilter.但是如果我在此之后尝试更改字符编码,它似乎总是会被覆盖.

import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.ws.rs.core.MediaType;

public class EnsureJsonResponseIsUtf8Filter implements Filter
{
    private class SimpleWrapper extends HttpServletResponseWrapper
    {
        public SimpleWrapper(HttpServletResponse response)
        {
            super(response);
        }

        @Override
        public String getCharacterEncoding()
        {
            return "UTF-8";
        }
    }

    @Override
    public void doFilter(ServletRequest request,ServletResponse response,FilterChain chain) throws IOException,ServletException
    {
        chain.doFilter(request,response);

        if (response.getContentType() != null && response.getContentType().contains(MediaType.APPLICATION_JSON))
        {
            response.setCharacterEncoding("UTF-8");
            chain.doFilter(request,new SimpleWrapper((HttpServletResponse) response));
        }
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException
    {
    }

    @Override
    public void destroy()
    {
    }
}

我见过其他similar questions,但他们似乎都没有这个问题.我已经尝试将我的过滤器注册为第一个,最后一个过滤器没有运气.

解决方法

import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.ws.rs.core.MediaType;

public class EnsureJsonIsUtf8ResponseFilter implements Filter
{
    final String APPLICATION_JSON_WITH_UTF8_CHARSET = MediaType.APPLICATION_JSON + ";charset=" + java.nio.charset.StandardCharsets.UTF_8;

    @Override
    public void doFilter(ServletRequest request,ServletException
    {
        HttpServletResponse r = (HttpServletResponse) response;
        HttpServletResponse wrappedResponse = new HttpServletResponseWrapper(r) 
        {
            @Override
            public ServletOutputStream getOutputStream() throws java.io.IOException
            {
                ServletResponse response = this.getResponse();

                String ct = (response != null) ? response.getContentType() : null;
                if (ct != null && ct.toLowerCase().startsWith(MediaType.APPLICATION_JSON))
                {
                    response.setContentType(APPLICATION_JSON_WITH_UTF8_CHARSET);
                }

                return super.getOutputStream();
            }
        };

        chain.doFilter(request,wrappedResponse); 
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException
    {
        // This method intentionally left blank
    }

    @Override
    public void destroy()
    {
        // This method intentionally left blank
    }
}

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