1.使用前提
需要在Filter过滤器doFilter方法中使用，使用示列：
@Override
public void doFilter(ServletRequest rq, ServletResponse rp, FilterChain chain){
HttpServletRequest request=(HttpServletRequest) rq;
HttpServletResponse response=(HttpServletResponse) rp;
//2.使用复制响应包装过滤器的响应执行chain.doFilter
HttpServletResponseCopier wrapper = new HttpServletResponseCopier(response);
try {
chain.doFilter(request, wrapper);
} catch (Exception e) {
//执行chain.doFilter(request, wrapper);时发生异常：
}
//3.(将截取的响应写出给过滤器的响应)一.截取向浏览器写入结果，二.写出响应给浏览器
String result = wrapper.writeResponse(response);
}
优势：
1.无需操心HttpServletResponse是PrintWriter还是OutputStream方式写出结果都可以获取到值。
2.使用简单依赖即用
其他注意事项：
该jar包是我私人的包，该包只有200多k 其中只有三个类，使用maven项目的小伙伴需要解压反编译后使用。
三个类我这里展示出来也可以去下载jar包 HttpServletResponseCopier：
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
public class HttpServletResponseCopier extends HttpServletResponseWrapper {
private ServletOutputStreamCopier streamCopier;
private PrintWriterCopier writerCopier;
//true=使用PrintWriterCopier；false=使用ServletOutputStreamCopier
private boolean useWriter;
private int statusCode;
public HttpServletResponseCopier(HttpServletResponse response) throws IOException {
super(response);
useWriter = true;
}
/**
* 复制response相应流（自动判断使用PrintWriter/OutputStream）
* @param response 接收浏览器请求时的响应HttpServletResponse结果对象
* @return response响应到浏览器内容
* @throws IOException
*/
public String writeResponse(HttpServletResponse response) throws IOException {
String rest="";
if (this.isUseWriter()) {
rest=new String(this.getWriterCopy());
PrintWriter out = response.getWriter();
out.write(this.getWriterCopy());
out.flush();
out.close();
} else {
rest=new String(this.getStreamCopy(),response.getCharacterEncoding());
OutputStream out = response.getOutputStream();
out.write(this.getStreamCopy());
out.flush();
out.close();
}
return rest;
}
@Override
public ServletOutputStream getOutputStream() throws IOException {
if (writerCopier != null) {
throw new IllegalStateException("getWriter() has already been called on this response.");
}
if (streamCopier == null) {
useWriter = false;
streamCopier = new ServletOutputStreamCopier();
}
return streamCopier;
}
@Override
public PrintWriter getWriter() throws IOException {
if (streamCopier != null) {
throw new IllegalStateException("getOutputStream() has already been called on this response.");
}
if (writerCopier == null) {
useWriter = true;
writerCopier = new PrintWriterCopier();
}
return writerCopier.getWriter();
}
public byte[] getBytes() {
if (streamCopier==null && writerCopier==null) {
return new byte[0];
}
return useWriter ? writerCopier.getBytes() : streamCopier.getCopy();
}
public byte[] getStreamCopy() {
if (useWriter) {
throw new IllegalStateException("already use writer, please call getWriterCopy()");
}
return streamCopier==null ? new byte[0] : streamCopier.getCopy();
}
public char[] getWriterCopy() {
if (!useWriter) {
throw new IllegalStateException("already use outputStream, please call getStreamCopy()");
}
return writerCopier==null ? new char[0] : writerCopier.getCopy();
}
/**
* The default behavior of this method is to call sendError(int sc, String msg)
* on the wrapped response object.
*/
public void sendError(int sc, String msg) throws IOException {
((HttpServletResponse)getResponse()).sendError(sc, msg);
this.statusCode = sc;
}
/**
* The default behavior of this method is to call sendError(int sc)
* on the wrapped response object.
*/
public void sendError(int sc) throws IOException {
((HttpServletResponse)getResponse()).sendError(sc);
this.statusCode = sc;
}
public void setStatus(int sc) {
super.setStatus(sc);
this.statusCode = sc;
}
/**
* The default behavior of this method is to call setStatus(int sc, String sm)
* on the wrapped response object.
*/
public void setStatus(int sc, String sm) {
super.setStatus(sc, sm);
this.statusCode = sc;
}
public int getStatus() {
return statusCode;
}
/**
* 是否使用PrintWriterCopier写出响应结果
* @return true=使用PrintWriterCopier；false=使用ServletOutputStreamCopier
*/
public boolean isUseWriter() {
return useWriter;
}
}
PrintWriterCopier
import java.io.CharArrayWriter;
import java.io.PrintWriter;
public class PrintWriterCopier {
private CharArrayWriter charArrayWriter;
private PrintWriter writer;
public PrintWriterCopier() {
this.charArrayWriter = new CharArrayWriter();
this.writer = new PrintWriter(charArrayWriter);
}
public PrintWriter getWriter() {
return writer;
}
public char[] getCopy() {
return charArrayWriter.toCharArray();
}
public byte[] getBytes() {
return charArrayWriter.toString().getBytes();
}
}
ServletOutputStreamCopier
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;
/**
* 拷贝Servlet输出
*
* Created by hai on 16/12/13.
*/
public class ServletOutputStreamCopier extends ServletOutputStream {
private static final int INIT_BUFFER_SIZE = 1024;
private ByteArrayOutputStream copy;
public ServletOutputStreamCopier() {
this.copy = new ByteArrayOutputStream(INIT_BUFFER_SIZE);
}
@Override
public void write(int b) throws IOException {
copy.write(b);
}
public byte[] getCopy() {
return copy.toByteArray();
}
@Override
public void flush() throws IOException {
copy.flush();
}
@Override
public boolean isReady() {
// TODO Auto-generated method stub
return false;
}
@Override
public void setWriteListener(WriteListener arg0) {
// TODO Auto-generated method stub
}
}
HttpServletResponseCopier下载jar
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