java下载文件到浏览器（java获取浏览器下载路径）

1. 增强HttpServletResponse对象1. 实现一个增强的HttpServletResponse类，需要继承javax.servlet.http.HttpServletRequestWrapper类，通过重写自己需要增强的方法来实现(这种模式就叫做装饰者模式)，使用该增强类在加上过滤器就可以实现无编码转换处理代码。public class MyRequest extends HttpServletRequestWrapper{ private HttpServletRequest req; public MyRequest(HttpServletRequest request) { super(request); req=request; } @Override public String getParameter(String name) { //解决编码问题，无论是post还是get请求，都不需要在业务代码中对编码再处理 String method=req.getMethod(); if("get".equalsIgnoreCase(method)){ try { String str=req.getParameter(name); byte[] b=str.getBytes("iso8859-1"); String newStr=new String(b, "utf-8"); return newStr; } catch (UnsupportedEncodingException e) { // TODO Auto-generated catch block e.printStackTrace(); } }else if("post".equalsIgnoreCase(method)){ try { req.setCharacterEncoding("utf-8"); } catch (UnsupportedEncodingException e) { // TODO Auto-generated catch block e.printStackTrace(); } } //不能删除此行代码,因为此行代码返回的就是编码之后的数据 return super.getParameter(name); }}在过滤器中应用public class FilterTest4 implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException {} @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { //生成增强的HttpServletRequest对象 HttpServletRequest req=(HttpServletRequest) request; MyRequest myReq=new MyRequest(req); //将增强的HttpServletRequest对象传入过滤器执行链中，在后面传入的request对象都会是增强的HttpServletRequest对象 chain.doFilter(myReq, response); } @Override public void destroy() {}}2. 文件上传原理过程1. JavaWeb中实现文件上传：客户端：HTML页面需要一个