CharResponseWrapper 捕获的内容为空

Question

我尝试了以下示例来替换我的 servlet 响应中的一些内容。

Programming Customized Requests and Responses

test.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8"></meta>
    <link th:href="@{/css/test.css}" rel="stylesheet"></link>
    <title>Test</title>
</head>
<body>
    <p class="forbiddenClass">Test!</p>
</body>
</html>

test.css:

.forbiddenClass {
    color: red;
}

CharResponseWrapper.java

public class CharResponseWrapper extends HttpServletResponseWrapper {

    private final CharArrayWriter output;

    public CharResponseWrapper(final HttpServletResponse response) {
        super(response);
        output = new CharArrayWriter();
    }

    public String toString() {
        return output.toString();
    }

    public PrintWriter getWriter() {
        return new PrintWriter(output);
    }
}

ClassReplacementFilter.java

@Component
public class ClassReplacementFilter extends GenericFilterBean {

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

        final CharResponseWrapper wrapper = new CharResponseWrapper((HttpServletResponse) response);
        chain.doFilter(request, wrapper);

        String content = wrapper.toString();
        if (StringUtils.isEmpty(content)) {
            System.out.println("content is empty for content type: " + response.getContentType());
        } else {
            content = content.replaceAll("forbiddenClass", "correctClass");
            response.setContentLength(content.getBytes().length);
            response.getOutputStream().write(content.getBytes());
        }
    }
}

如您所见，我想将字符串 forbiddenClass 替换为 correctClass，但它仅适用于 html 文件。 test.css的内容不变，打印出filter的如下信息。

content is empty for content type: text/css;charset=UTF-8

为什么test.css的内容是空的？

Answer 1

Why is the content empty for test.css?

因为您只捕获了写入 response.getWriter() 的内容，而不捕获写入 response.getOutputStream() 的内容。

您需要 HttpServletResponseWrapper 实现，如相关问题答案底部所示：Catch-all servlet filter that should capture ALL HTML input content for manipulation, works only intermittently。

CharResponseWrapper 捕获的内容为空

CharResponseWrapper captured content is empty

spring

servlets

servlet-filters