我想对 HTTP 响应(json 格式)执行一些过滤逻辑。
我已成功更改响应正文,但是当正文的(字符串)大小发生变化时:我丢失了最后一个字符。
为了更简单,我创建了一个简单的 Spring Boot 应用程序,仅对我的其余 Controller 进行 Web 依赖。
我的休息 Controller
@RestController
@RequestMapping("/home/")
public class RestControllerHome {
@GetMapping (produces=MediaType.APPLICATION_JSON_VALUE)
public String home() {
return "{ \"name\" : \"Peter\" }";
}
}
我的过滤器
@Component
public class MyFilter implements Filter {
@Override
public void destroy() { }
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {
HtmlResponseWrapper capturingResponseWrapper = new HtmlResponseWrapper((HttpServletResponse) response);
filterChain.doFilter(request, capturingResponseWrapper);
if (response.getContentType() != null && response.getContentType().contains("application/json")) {
String content = capturingResponseWrapper.getCaptureAsString();
// This code works fine
//response.getWriter().write(content.toUpperCase());
// This code doesn't works because the content size is changed
response.getWriter().write("{ \"name\" : \"************r\" }");
}
}
@Override
public void init(FilterConfig arg0) throws ServletException { }
}
HttpServletResponseWrapper //在写入之前捕获响应
public class HtmlResponseWrapper extends HttpServletResponseWrapper {
private final ByteArrayOutputStream capture;
private ServletOutputStream output;
private PrintWriter writer;
public HtmlResponseWrapper(HttpServletResponse response) {
super(response);
capture = new ByteArrayOutputStream(response.getBufferSize());
}
@Override
public ServletOutputStream getOutputStream() {
if (writer != null) {
throw new IllegalStateException("getWriter() has already been called on this response.");
}
if (output == null) {
// inner class - lets the wrapper manipulate the response
output = new ServletOutputStream() {
@Override
public void write(int b) throws IOException {
capture.write(b);
}
@Override
public void flush() throws IOException {
capture.flush();
}
@Override
public void close() throws IOException {
capture.close();
}
@Override
public boolean isReady() {
return false;
}
@Override
public void setWriteListener(WriteListener arg0) {
}
};
}
return output;
}
@Override
public PrintWriter getWriter() throws IOException {
if (output != null) {
throw new IllegalStateException("getOutputStream() has already been called on this response.");
}
if (writer == null) {
writer = new PrintWriter(new OutputStreamWriter(capture,
getCharacterEncoding()));
}
return writer;
}
@Override
public void flushBuffer() throws IOException {
super.flushBuffer();
if (writer != null) {
writer.flush();
} else if (output != null) {
output.flush();
}
}
public byte[] getCaptureAsBytes() throws IOException {
if (writer != null) {
writer.close();
} else if (output != null) {
output.close();
}
return capture.toByteArray();
}
public String getCaptureAsString() throws IOException {
return new String(getCaptureAsBytes(), getCharacterEncoding());
}
}
在我的doFilter方法中,以下代码...
// This code works fine
response.getWriter().write(content.toUpperCase());
// This code doesn't works because the content size is changed
//response.getWriter().write("{ \"name\" : \"************r\" }");
...给出了以下输出: {"NAME": "PETER"} 这告诉我,代码工作正常。
但是,实际上我想更改正文内容......
// This code works fine
//response.getWriter().write(content.toUpperCase());
// This code doesn't works because the content size is changed
response.getWriter().write("{ \"name\" : \"************r\" }");
...以及前面的代码,给我一个不完整的文本正文作为输出: **{“姓名”:“************
我做错了什么? 我的应用程序有一个更大的 json 主体,并且过滤器中的逻辑更复杂一些。但是,如果我不能让这个工作,我就无法让我的代码的其余部分工作。请帮忙。
我从 https://www.leveluplunch.com/java/tutorials/034-modify-html-response-using-filter/ 获取了 Filter 和 HttpServletResponseWrapper
最佳答案
感谢JBNizet的帮助,我发现解决方案是添加Content Lenght:
String newContent = "{ \"name\" : \"************r\" }";
response.setContentLength(newContent .length());
response.getWriter().write(newContent);
关于java - 如何使用java过滤器修改响应主体?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/51826475/