前言
只有光头才能变强。
文本已收录至我的GitHub仓库，欢迎Star：https://github.com/ZhongFuCheng3y/3y
在上篇博文中，我们已经讲解了过滤器的基本概念，使用以及简单的Servlet应用了。这篇博文主要讲解过滤器的高级应用。。
编码过滤器
目的：解决全站的乱码问题
开发过滤器
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException { //将request和response强转成http协议的 HttpServletRequest httpServletRequest = (HttpServletRequest) req; HttpServletResponse httpServletResponse = (HttpServletResponse) resp; httpServletRequest.setCharacterEncoding("UTF-8"); httpServletResponse.setCharacterEncoding("UTF-8"); httpServletResponse.setContentType("text/html;charset=UTF-8"); chain.doFilter(httpServletRequest, httpServletResponse);}
//将request和response强转成http协议的
HttpServletRequest httpServletRequest = (HttpServletRequest) req;
HttpServletResponse httpServletResponse = (HttpServletResponse) resp;
httpServletRequest.setCharacterEncoding("UTF-8");
httpServletResponse.setCharacterEncoding("UTF-8");
httpServletResponse.setContentType("text/html;charset=UTF-8");
chain.doFilter(httpServletRequest, httpServletResponse);
}
第一次测试
Servlet1中向浏览器回应中文数据，没有出现乱码。
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.getWriter().write("看完博客点赞！");}
response.getWriter().write("看完博客点赞！");
}
分析
上面的过滤器是不完善的，因为浏览器用get方式提交给服务器的中文数据，单单靠上面的过滤器是无法完成的！
那么我们需要怎么做呢？？我们之前解决get方式的乱码问题是这样的：使用request获取传递过来的数据，经过ISO 8859-1反编码获取得到不是乱码的数据（传到Servlet上的数据已经被ISO 8859-1编码过了，反编码就可以获取原来的数据），再用UTF-8编码，得到中文数据！
在Servlet获取浏览器以GET方式提交过来的中文是乱码的根本原因是：getParameter()方法是以ISO 8859-1的编码来获取浏览器传递过来的数据的，得到的是乱码
既然知道了根本原因，那也好办了：过滤器传递的request对象，使用getParameter()方法的时候，获取得到的是正常的中文数据
也就是说，sun公司为我们提供的request对象是不够用的，因为sun公司提供的request对象使用getParameter()获取get方式提交过来的数据是乱码，于是我们要增强request对象（使得getParameter()获取得到的是中文）！
增强request对象
增强request对象，我们要使用包装设计模式！
包装设计模式的五个步骤：
sun公司也知道我们可能对request对象的方法不满意，于是提供了HttpServletRequestWrapper类给我们实现（如果实现HttpServletRequest接口的话，要实现太多的方法了！）
class MyRequest extends HttpServletRequestWrapper { private HttpServletRequest request; public MyRequest(HttpServletRequest request) { super(request); this.request = request; } @Override public String getParameter(String name) { String value = this.request.getParameter(name); if (value == null) { return null; } //如果不是get方法的，直接返回就行了 if (!this.request.getMethod().equalsIgnoreCase("get")) { return null; } try { //进来了就说明是get方法，把乱码的数据 value = new String(value.getBytes("ISO8859-1"), this.request.getCharacterEncoding()); return value ; } catch (UnsupportedEncodingException e) { e.printStackTrace(); throw new RuntimeException("不支持该编码"); } }}
private HttpServletRequest request;
public MyRequest(HttpServletRequest request) {
super(request);
this.request = request;
}
@Override
public String getParameter(String name) {
String value = this.request.getParameter(name);
if (value == null) {
return null;
}
//如果不是get方法的，直接返回就行了
if (!this.request.getMethod().equalsIgnoreCase("get")) {
return null;
}
try {
//进来了就说明是get方法，把乱码的数据
value = new String(value.getBytes("ISO8859-1"), this.request.getCharacterEncoding());
return value ;
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
throw new RuntimeException("不支持该编码");
}
}
}
将被增强的request对象传递给目标资源，那么目标资源使用request调用getParameter()方法的时候，获取得到的就是中文数据，而不是乱码了！
//将request和response强转成http协议的HttpServletRequest httpServletRequest = (HttpServletRequest) req;HttpServletResponse httpServletResponse = (HttpServletResponse) resp;httpServletRequest.setCharacterEncoding("UTF-8");httpServletResponse.setCharacterEncoding("UTF-8");httpServletResponse.setContentType("text/html;charset=UTF-8");MyRequest myRequest = new MyRequest(httpServletRequest);//传递给目标资源的request是被增强后的。chain.doFilter(myRequest, httpServletResponse);
HttpServletRequest httpServletRequest = (HttpServletRequest) req;
HttpServletResponse httpServletResponse = (HttpServletResponse) resp;
httpServletRequest.setCharacterEncoding("UTF-8");
httpServletResponse.setCharacterEncoding("UTF-8");
httpServletResponse.setContentType("text/html;charset=UTF-8");
MyRequest myRequest = new MyRequest(httpServletRequest);
//传递给目标资源的request是被增强后的。
chain.doFilter(myRequest, httpServletResponse);
第二次测试
<form action="${pageContext.request.contextPath}/Servlet1" method="get"> <input type="hidden" name="username" value="中国"> <input type="submit" value="提交"></form>
<input type="hidden" name="username" value="中国">
<input type="submit" value="提交">
</form>
敏感词的过滤器
如果用户输入了敏感词（傻b、尼玛、操蛋等等不文明语言时），我们要将这些不文明用于屏蔽掉，替换成符号！
要实现这样的功能也很简单，用户输入的敏感词肯定是在getParameter()获取的，我们在getParameter()得到这些数据的时候，判断有没有敏感词汇，如果有就替换掉就好了！简单来说：也是要增强request对象
增强request对象
class MyDirtyRequest extends HttpServletRequestWrapper { HttpServletRequest request; //定义一堆敏感词汇 private List<String> list = Arrays.asList("傻b", "尼玛", "操蛋"); public MyDirtyRequest(HttpServletRequest request) { super(request); this.request = request; } @Override public String getParameter(String name) { String value = this.request.getParameter(name); if (value == null) { return null; } //遍历list集合，看看获取得到的数据有没有敏感词汇 for (String s : list) { if (s.equals(value)) { value = "*****"; } } return value ; }}
HttpServletRequest request;
//定义一堆敏感词汇
private List<String> list = Arrays.asList("傻b", "尼玛", "操蛋");
public MyDirtyRequest(HttpServletRequest request) {
super(request);
this.request = request;
}
@Override
public String getParameter(String name) {
String value = this.request.getParameter(name);
if (value == null) {
return null;
}
//遍历list集合，看看获取得到的数据有没有敏感词汇
for (String s : list) {
if (s.equals(value)) {
value = "*****";
}
}
return value ;
}
}
开发过滤器
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException { //将request和response强转成http协议的 HttpServletRequest httpServletRequest = (HttpServletRequest) req; HttpServletResponse httpServletResponse = (HttpServletResponse) resp; MyDirtyRequest dirtyRequest = new MyDirtyRequest(httpServletRequest); //传送给目标资源的是被增强后的request对象 chain.doFilter(dirtyRequest, httpServletResponse);}
//将request和response强转成http协议的
HttpServletRequest httpServletRequest = (HttpServletRequest) req;
HttpServletResponse httpServletResponse = (HttpServletResponse) resp;
MyDirtyRequest dirtyRequest = new MyDirtyRequest(httpServletRequest);
//传送给目标资源的是被增强后的request对象
chain.doFilter(dirtyRequest, httpServletResponse);
}
测试
压缩资源过滤器
按照过滤器的执行顺序：执行完目标资源，过滤器后面的代码还会执行。所以，我们在过滤器中可以获取执行完目标资源后的response对象！
我们知道sun公司提供的response对象调用write()方法，是直接把数据返回给浏览器的。我们要想实现压缩的功能，write()方法就不能直接把数据写到浏览器上！
这和上面是类似的，过滤器传递给目标资源的response对象就需要被我们增强，使得目标资源调用writer()方法的时候不把数据直接写到浏览器上！
增强response对象
response对象可能会使用PrintWriter或者ServletOutputStream对象来调用writer()方法的，所以我们增强response对象的时候，需要把getOutputSteam和getWriter()重写
class MyResponse extends HttpServletResponseWrapper{ HttpServletResponse response; public MyResponse(HttpServletResponse response) { super(response); this.response = response; } @Override public ServletOutputStream getOutputStream() throws IOException { return super.getOutputStream(); } @Override public PrintWriter getWriter() throws IOException { return super.getWriter(); }}
HttpServletResponse response;
public MyResponse(HttpServletResponse response) {
super(response);
this.response = response;
}
@Override
public ServletOutputStream getOutputStream() throws IOException {
return super.getOutputStream();
}
@Override
public PrintWriter getWriter() throws IOException {
return super.getWriter();
}
}
接下来，ServletOutputSteam要调用writer()方法，使得它不会把数据写到浏览器上。这又要我们增强一遍了！
增强ServletOutputSteam
/*增强ServletOutputSteam，让writer方法不把数据直接返回给浏览器*/class MyServletOutputStream extends ServletOutputStream{ private ByteArrayOutputStream byteArrayOutputStream; public MyServletOutputStream(ByteArrayOutputStream byteArrayOutputStream) { this.byteArrayOutputStream = byteArrayOutputStream; } //当调用write()方法的时候，其实是把数据写byteArrayOutputSteam上 @Override public void write(int b) throws IOException { this.byteArrayOutputStream.write(b); }}
class MyServletOutputStream extends ServletOutputStream{
private ByteArrayOutputStream byteArrayOutputStream;
public MyServletOutputStream(ByteArrayOutputStream byteArrayOutputStream) {
this.byteArrayOutputStream = byteArrayOutputStream;
}
//当调用write()方法的时候，其实是把数据写byteArrayOutputSteam上
@Override
public void write(int b) throws IOException {
this.byteArrayOutputStream.write(b);
}
}
增强PrintWriter
PrintWriter对象就好办了，它本来就是一个包装类，看它的构造方法，我们直接可以把ByteArrayOutputSteam传递给PrintWriter上。
@Overridepublic PrintWriter getWriter() throws IOException { printWriter = new PrintWriter(new OutputStreamWriter(byteArrayOutputStream, this.response.getCharacterEncoding())); return printWriter;}
public PrintWriter getWriter() throws IOException {
printWriter = new PrintWriter(new OutputStreamWriter(byteArrayOutputStream, this.response.getCharacterEncoding()));
return printWriter;
}
获取缓存数据
我们把数据都写在了ByteArrayOutputSteam上了，应该提供方法给外界过去缓存中的数据！
public byte[] getBuffer() { try { //防止数据在缓存中，要刷新一下！ if (printWriter != null) { printWriter.close(); } if (byteArrayOutputStream != null) { byteArrayOutputStream.flush(); return byteArrayOutputStream.toByteArray(); } } catch (IOException e) { e.printStackTrace(); } return null;}byte[] getBuffer() {
try {
//防止数据在缓存中，要刷新一下！
if (printWriter != null) {
printWriter.close();
}
if (byteArrayOutputStream != null) {
byteArrayOutputStream.flush();
return byteArrayOutputStream.toByteArray();
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
增强response的完整代码
class MyResponse extends HttpServletResponseWrapper{ private ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(); private PrintWriter printWriter ; private HttpServletResponse response; public MyResponse(HttpServletResponse response) { super(response); this.response = response; } @Override public ServletOutputStream getOutputStream() throws IOException { //这个的ServletOutputSteam对象调用write()方法的时候，把数据是写在byteArrayOutputSteam上的 return new MyServletOutputStream(byteArrayOutputStream); } @Override public PrintWriter getWriter() throws IOException { printWriter = new PrintWriter(new OutputStreamWriter(byteArrayOutputStream, this.response.getCharacterEncoding())); return printWriter; } public byte[] getBuffer() { try { //防止数据在缓存中，要刷新一下！ if (printWriter != null) { printWriter.close(); } if (byteArrayOutputStream != null) { byteArrayOutputStream.flush(); return byteArrayOutputStream.toByteArray(); } } catch (IOException e) { e.printStackTrace(); } return null; }}
private ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
private PrintWriter printWriter ;
private HttpServletResponse response;
public MyResponse(HttpServletResponse response) {
super(response);
this.response = response;
}
@Override
public ServletOutputStream getOutputStream() throws IOException {
//这个的ServletOutputSteam对象调用write()方法的时候，把数据是写在byteArrayOutputSteam上的
return new MyServletOutputStream(byteArrayOutputStream);
}
@Override
public PrintWriter getWriter() throws IOException {
printWriter = new PrintWriter(new OutputStreamWriter(byteArrayOutputStream, this.response.getCharacterEncoding()));
return printWriter;
}
public byte[] getBuffer() {
try {
//防止数据在缓存中，要刷新一下！
if (printWriter != null) {
printWriter.close();
}
if (byteArrayOutputStream != null) {
byteArrayOutputStream.flush();
return byteArrayOutputStream.toByteArray();
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
过滤器
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException { HttpServletRequest request = (HttpServletRequest) req; HttpServletResponse response = (HttpServletResponse) resp; MyResponse myResponse = new MyResponse(response); //把被增强的response对象传递进去，目标资源调用write()方法的时候就不会直接把数据写在浏览器上了 chain.doFilter(request, myResponse); //得到目标资源想要返回给浏览器的数据 byte[] bytes = myResponse.getBuffer(); //输出原来的大小 System.out.println("压缩前："+bytes.length); //使用GZIP来压缩资源，再返回给浏览器 ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(); GZIPOutputStream gzipOutputStream = new GZIPOutputStream(byteArrayOutputStream); gzipOutputStream.write(bytes); //得到压缩后的数据 byte[] gzip = byteArrayOutputStream.toByteArray(); System.out.println("压缩后：" + gzip.length); //还要设置头，告诉浏览器，这是压缩数据！ response.setHeader("content-encoding", "gzip"); response.setContentLength(gzip.length); response.getOutputStream().write(gzip);}
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
MyResponse myResponse = new MyResponse(response);
//把被增强的response对象传递进去，目标资源调用write()方法的时候就不会直接把数据写在浏览器上了
chain.doFilter(request, myResponse);
//得到目标资源想要返回给浏览器的数据
byte[] bytes = myResponse.getBuffer();
//输出原来的大小
System.out.println("压缩前："+bytes.length);
//使用GZIP来压缩资源，再返回给浏览器
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
GZIPOutputStream gzipOutputStream = new GZIPOutputStream(byteArrayOutputStream);
gzipOutputStream.write(bytes);
//得到压缩后的数据
byte[] gzip = byteArrayOutputStream.toByteArray();
System.out.println("压缩后：" + gzip.length);
//还要设置头，告诉浏览器，这是压缩数据！
response.setHeader("content-encoding", "gzip");
response.setContentLength(gzip.length);
response.getOutputStream().write(gzip);
}
测试
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.getWriter().write("fdshfidsuhfidusfhuidsfhuidshdsuifhsd" + "uifhsduifffffdshfidsuhfidusfhuidsfhuidshdsuif" + "hsduifhsduifffffdshfidsuhfidusfhuidsfhuidshd" + "suifhsduifhsduifffffdshfidsuhfidusfhuidsfhuidsh" + "dsuifhsduifhsduifffffdshfidsuhfidusfhuidsfhuids" + "hdsuifhsduifhsduifffffdshfidsuhfidusfhuidsfhuid" + "shdsuifhsduifhsduiffdshfidsuhfidusfhuidsfhuids" + "hdsuifhsduifhsduifffffdshfidsuhfidusfhuidsfhui" + "dshdsuifhsduifhsduifffffdshfidsuhfidusfhuidsfh" + "uidshdsuifhsduifhsduifffffdshfidsuhfidusfhuids" + "fhuidshdsuifhsduifhsduifffffdshfidsuhfidusfhuid" + "sfhuidshdsuifhsduifhsduifffffdshfidsuhfidusfhui" + "dsfhuidshdsuifhsduifhsduifffffdshfidsuhfidusfh" + "uidsfhuidshdsuifhsduifhsduifffffdshfidsuhfidusf" + "huidsfhuidshdsuifhsduifhsduifffffdshfidsuhfidus" + "fhuidsfhuidshdsuifhsduifhsduifffffdshfidsuhfid" + "usfhuidsfhuidshdsuifhsduifhsduifffffdshfidsuhf" + "idusfhuidsfhuidshdsuifhsduifhsd" + "uifffffdshfidsuhfidusfhuidsfhuidshdsuifhsduifhsduifffffff");}
response.getWriter().write("fdshfidsuhfidusfhuidsfhuidshdsuifhsd" +
"uifhsduifffffdshfidsuhfidusfhuidsfhuidshdsuif" +
"hsduifhsduifffffdshfidsuhfidusfhuidsfhuidshd" +
"suifhsduifhsduifffffdshfidsuhfidusfhuidsfhuidsh" +
"dsuifhsduifhsduifffffdshfidsuhfidusfhuidsfhuids" +
"hdsuifhsduifhsduifffffdshfidsuhfidusfhuidsfhuid" +
"shdsuifhsduifhsduiffdshfidsuhfidusfhuidsfhuids" +
"hdsuifhsduifhsduifffffdshfidsuhfidusfhuidsfhui" +
"dshdsuifhsduifhsduifffffdshfidsuhfidusfhuidsfh" +
"uidshdsuifhsduifhsduifffffdshfidsuhfidusfhuids" +
"fhuidshdsuifhsduifhsduifffffdshfidsuhfidusfhuid" +
"sfhuidshdsuifhsduifhsduifffffdshfidsuhfidusfhui" +
"dsfhuidshdsuifhsduifhsduifffffdshfidsuhfidusfh" +
"uidsfhuidshdsuifhsduifhsduifffffdshfidsuhfidusf" +
"huidsfhuidshdsuifhsduifhsduifffffdshfidsuhfidus" +
"fhuidsfhuidshdsuifhsduifhsduifffffdshfidsuhfid" +
"usfhuidsfhuidshdsuifhsduifhsduifffffdshfidsuhf" +
"idusfhuidsfhuidshdsuifhsduifhsd" +
"uifffffdshfidsuhfidusfhuidsfhuidshdsuifhsduifhsduifffffff");
}
HTML转义过滤器
只要把getParameter()获取得到的数据转义一遍，就可以完成功能了。
增强request
class MyHtmlRequest extends HttpServletRequestWrapper{ private HttpServletRequest request; public MyHtmlRequest(HttpServletRequest request) { super(request); this.request = request; } @Override public String getParameter(String name) { String value = this.request.getParameter(name); return this.Filter(value); } public String Filter(String message) { if (message == null) return (null); char content[] = new char[message.length()]; message.getChars(0, message.length(), content, 0); StringBuffer result = new StringBuffer(content.length + 50); for (int i = 0; i < content.length; i++) { switch (content[i]) { case '<': result.append("<"); break; case '>': result.append(">"); break; case '&': result.append("&"); break; case '"': result.append("""); break; default: result.append(content[i]); } } return (result.toString()); }}
private HttpServletRequest request;
public MyHtmlRequest(HttpServletRequest request) {
super(request);
this.request = request;
}
@Override
public String getParameter(String name) {
String value = this.request.getParameter(name);
return this.Filter(value);
}
public String Filter(String message) {
if (message == null)
return (null);
char content[] = new char[message.length()];
message.getChars(0, message.length(), content, 0);
StringBuffer result = new StringBuffer(content.length + 50);
for (int i = 0; i < content.length; i++) {
switch (content[i]) {
case '<':
result.append("<");
break;
case '>':
result.append(">");
break;
case '&':
result.append("&");
break;
case '"':
result.append(""");
break;
default:
result.append(content[i]);
}
}
return (result.toString());
}
}
过滤器
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException { HttpServletRequest request = (HttpServletRequest) req; HttpServletResponse response = (HttpServletResponse) resp; MyHtmlRequest myHtmlRequest = new MyHtmlRequest(request); //传入的是被增强的request！ chain.doFilter(myHtmlRequest, response);}
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
MyHtmlRequest myHtmlRequest = new MyHtmlRequest(request);
//传入的是被增强的request！
chain.doFilter(myHtmlRequest, response);
}
测试
jsp代码：
<form action="${pageContext.request.contextPath}/Servlet1" method="post"> <input type="hidden" name="username" value="<h1>你好i好<h1>"> <input type="submit" value="提交"></form>
<input type="hidden" name="username" value="<h1>你好i好<h1>">
<input type="submit" value="提交">
</form>
Servlet代码：
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String value = request.getParameter("username"); response.getWriter().write(value);}
String value = request.getParameter("username");
response.getWriter().write(value);
}
缓存数据到内存中
在前面我们已经做过了，让浏览器不缓存数据【验证码的图片是不应该缓存的】。
现在我们要做的是：缓存数据到内存中【如果某个资源重复使用，不轻易变化，应该缓存到内存中】
这个和压缩数据的Filter非常类似的，因为让数据不直接输出给浏览器，把数据用一个容器（ByteArrayOutputSteam）存起来。如果已经有缓存了，就取缓存的。没有缓存就执行目标资源！
增强response对象
class MyResponse extends HttpServletResponseWrapper { private ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(); private PrintWriter printWriter ; private HttpServletResponse response; public MyResponse(HttpServletResponse response) { super(response); this.response = response; } @Override public ServletOutputStream getOutputStream() throws IOException { //这个的ServletOutputSteam对象调用write()方法的时候，把数据是写在byteArrayOutputSteam上的 return new MyServletOutputStream(byteArrayOutputStream); } @Override public PrintWriter getWriter() throws IOException { printWriter = new PrintWriter(new OutputStreamWriter(byteArrayOutputStream, this.response.getCharacterEncoding())); return printWriter; } public byte[] getBuffer() { try { //防止数据在缓存中，要刷新一下！ if (printWriter != null) { printWriter.close(); } if (byteArrayOutputStream != null) { byteArrayOutputStream.flush(); return byteArrayOutputStream.toByteArray(); } } catch (IOException e) { e.printStackTrace(); } return null; }}//增强ServletOutputSteam，让writer方法不把数据直接返回给浏览器class MyServletOutputStream extends ServletOutputStream { private ByteArrayOutputStream byteArrayOutputStream; public MyServletOutputStream(ByteArrayOutputStream byteArrayOutputStream) { this.byteArrayOutputStream = byteArrayOutputStream; } //当调用write()方法的时候，其实是把数据写byteArrayOutputSteam上 @Override public void write(int b) throws IOException { this.byteArrayOutputStream.write(b); }}
private ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
private PrintWriter printWriter ;
private HttpServletResponse response;
public MyResponse(HttpServletResponse response) {
super(response);
this.response = response;
}
@Override
public ServletOutputStream getOutputStream() throws IOException {
//这个的ServletOutputSteam对象调用write()方法的时候，把数据是写在byteArrayOutputSteam上的
return new MyServletOutputStream(byteArrayOutputStream);
}
@Override
public PrintWriter getWriter() throws IOException {
printWriter = new PrintWriter(new OutputStreamWriter(byteArrayOutputStream, this.response.getCharacterEncoding()));
return printWriter;
}
public byte[] getBuffer() {
try {
//防止数据在缓存中，要刷新一下！
if (printWriter != null) {
printWriter.close();
}
if (byteArrayOutputStream != null) {
byteArrayOutputStream.flush();
return byteArrayOutputStream.toByteArray();
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
//增强ServletOutputSteam，让writer方法不把数据直接返回给浏览器
class MyServletOutputStream extends ServletOutputStream {
private ByteArrayOutputStream byteArrayOutputStream;
public MyServletOutputStream(ByteArrayOutputStream byteArrayOutputStream) {
this.byteArrayOutputStream = byteArrayOutputStream;
}
//当调用write()方法的时候，其实是把数据写byteArrayOutputSteam上
@Override
public void write(int b) throws IOException {
this.byteArrayOutputStream.write(b);
}
}
过滤器
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException { //定义一个Map集合，key为页面的地址，value为内存的缓存 Map<String, byte[]> map = new HashMap<>(); HttpServletRequest request = (HttpServletRequest) req; HttpServletResponse response = (HttpServletResponse) resp; //得到客户端想要请求的资源 String uri = request.getRequestURI(); byte[] bytes = map.get(uri); //如果有缓存，直接返回给浏览器就行了，就不用执行目标资源了 if (bytes != null) { response.getOutputStream().write(bytes); return ; } //如果没有缓存，就让目标执行 MyResponse myResponse = new MyResponse(response); chain.doFilter(request, myResponse); //得到目标资源想要发送给浏览器的数据 byte[] b = myResponse.getBuffer(); //把数据存到集合中 map.put(uri, b); //把数据返回给浏览器 response.getOutputStream().write(b);}
//定义一个Map集合，key为页面的地址，value为内存的缓存
Map<String, byte[]> map = new HashMap<>();
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
//得到客户端想要请求的资源
String uri = request.getRequestURI();
byte[] bytes = map.get(uri);
//如果有缓存，直接返回给浏览器就行了，就不用执行目标资源了
if (bytes != null) {
response.getOutputStream().write(bytes);
return ;
}
//如果没有缓存，就让目标执行
MyResponse myResponse = new MyResponse(response);
chain.doFilter(request, myResponse);
//得到目标资源想要发送给浏览器的数据
byte[] b = myResponse.getBuffer();
//把数据存到集合中
map.put(uri, b);
//把数据返回给浏览器
response.getOutputStream().write(b);
}
测试
尽管是刷新，获取得到的也是从缓存拿到的数据！
最后
乐于输出干货的Java技术公众号：Java3y。公众号内有200多篇原创技术文章、海量视频资源、精美脑图，不妨来关注一下！
352
扫一扫
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
