response保存了请求的返回信息,里面有个outputstream,你要返回给页面的流,都在这个地方保存. 之前遇到一个问题,想把outputstream修改一下.因为这是个输出流,想要改这个里面的东西不是这么简单的. sun为我们提供了这么一个工具HttpServletResponseWrapper抽象类,利用这个类的子类把servletresponse包装一下,在过滤器中使用,就可以去除response的文件流,对其作出修改.给出一个实现:
代码语言：javascript复制import javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.*;
/**
* ResponseWrapper
*
* @author wuweifeng
* @version 1.0
* @date 2021-08-16
*/
public class ResponseWrapper extends HttpServletResponseWrapper {
/**
* ByteArrayOutputStream
*/
private ByteArrayOutputStream buffer;
/**
* ServletOutputStream
*/
private ServletOutputStream out;
/**
* writer
*/
private PrintWriter writer;
/**
* ResponseWrapper
*/
public ResponseWrapper(HttpServletResponse resp) throws IOException {
super(resp);
buffer = new ByteArrayOutputStream();//真正存储数据的流
out = new WrapperOutputStream(buffer);
writer = new PrintWriter(new OutputStreamWriter(buffer, this.getCharacterEncoding()));
}
//重载父类获取outputstream的方法
@Override
public ServletOutputStream getOutputStream() throws IOException {
return out;
}
//重载父类获取writer的方法
@Override
public PrintWriter getWriter() throws UnsupportedEncodingException {
return writer;
}
//重载父类获取flushBuffer的方法
@Override
public void flushBuffer() throws IOException {
if (out != null) {
out.flush();
}
if (writer != null) {
writer.flush();
}
}
@Override
public void reset() {
buffer.reset();
}
/**
* 获取response的字符串
*/
public String getContent() throws IOException {
flushBuffer();//将out、writer中的数据强制输出到WapperedResponse的buffer里面，否则取不到数据
return new String(buffer.toByteArray());
}
//内部类，对ServletOutputStream进行包装
private class WrapperOutputStream extends ServletOutputStream {
/**
* ByteArrayOutputStream
*/
private ByteArrayOutputStream bos;
/**
* WrapperOutputStream
*/
WrapperOutputStream(ByteArrayOutputStream stream) {
bos = stream;
}
@Override
public void write(int b) {
bos.write(b);
}
@Override
public boolean isReady() {
return false;
}
@Override
public void setWriteListener(WriteListener writeListener) {
}
}
}然后在你的过滤器中这么使用:
代码语言：javascript复制public class UserFilter implements Filter {
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
HttpServletResponse resp = (HttpServletResponse) servletResponse;
ResponseWrapper mResp = new ResponseWrapper(resp);// 包装响应对象 resp 并缓存响应数据
filterChain.doFilter(servletRequest, mResp);
String content = mResp.getContent();//response流的内容
System.out.println(content);
//此处可以对content做处理,然后再把content写回到输出流中
servletResponse.setContentLength(-1);
PrintWriter out = servletResponse.getWriter();
out.write(content);
out.flush();
out.close();
}
}关于入参request的，如果只是key-value型的，对应客户端是form那种传过来的，在filter里直接获取没事。但如果是application/json型的，如果这个输入流被提前读取了，则后续真正的controller就取不到了，也需要做个包装类。
代码语言：javascript复制import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import static com.alibaba.fastjson.util.IOUtils.UTF8;
public class RequestWrapper extends HttpServletRequestWrapper {
/**
* log
*/
private static final Logger log = LoggerFactory.getLogger(RequestWrapper.class);
/**
* application/json型的入参
*/
private final String body;
/**
* key-value型所有的入参
*/
private Map<String, String[]> params = new HashMap<>();
public RequestWrapper(HttpServletRequest request) {
super(request);
this.params.putAll(request.getParameterMap());
StringBuilder stringBuilder = new StringBuilder();
BufferedReader bufferedReader = null;
InputStream inputStream = null;
try {
inputStream = request.getInputStream();
if (inputStream != null) {
bufferedReader = new BufferedReader(new InputStreamReader(inputStream, UTF8));
char[] charBuffer = new char[512];
int bytesRead;
while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
stringBuilder.append(charBuffer, 0, bytesRead);
}
}
} catch (IOException ex) {
log.error("requestBody read error ignore,message:" ex.getMessage());
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
log.error("requestBody inputStream close error,ignore");
}
}
if (bufferedReader != null) {
try {
bufferedReader.close();
} catch (IOException e) {
log.error("requestBody bufferedReader close error,ignore");
}
}
}
body = stringBuilder.toString();
}
@Override
public ServletInputStream getInputStream() throws IOException {
final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(body.getBytes(UTF8));
ServletInputStream servletInputStream = new ServletInputStream() {
@Override
public boolean isFinished() {
return false;
}
@Override
public boolean isReady() {
return false;
}
@Override
public void setReadListener(ReadListener readListener) {
}
@Override
public int read() throws IOException {
return byteArrayInputStream.read();
}
};
return servletInputStream;
}
@Override
public BufferedReader getReader() throws IOException {
return new BufferedReader(new InputStreamReader(this.getInputStream(), UTF8));
}
public String getBody() {
return this.body;
}
@Override
public String getParameter(String name) {
String[] values = params.get(name);
if (values == null || values.length == 0) {
return null;
}
return values[0];
}
@Override
public String[] getParameterValues(String name) {
return params.get(name);
}
@Override
public Enumeration<String> getParameterNames() {
return Collections.enumeration(params.keySet());
}
}
