java如何将列表从servlet写入。文本

1 年 Questions & Answers 517

我创建了一个servlet，它滚动10个随机值，排序并打印这个值。此值正在添加到LinkedList。如何将数据从LinkedList保存到文件。txt时，应用程序将关闭。我尝试在servlet中创建文件并编写一些东西，但我的代码没有创建文件

    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();
    try {
        /* TODO output your page here. You may use following sample code. */
        out.println("<html>");
        out.println("<head>");
        out.println("<title>Servlet NewServlet</title>");            
        out.println("</head>");
        out.println("<body>");
        out.println("<h1>Servlet NewServlet at " + request.getContextPath() + "</h1>");
        List<Integer> lista=(List<Integer>) this.getServletContext().getAttribute("lista");
        out.println("<ul>");
        for(Integer l:lista){
            out.println("<li>"+l+"</li>");
        }
        out.println("</ul>");
        out.println("<form action=\"NewServlet1\">");
        out.println("<input type=\"text\" name=\"liczba\">");
        out.println("<input type=\"submit\" value=\"ADD\">");
        out.println("</form>");
        out.println("</body>");
        out.println("</html>");
    } finally {            
        out.close();
    }

        PrintWriter zapis = null;
        zapis = new PrintWriter("test.txt");
        zapis.println("type type type ");
        zapis.close();


}

public class NewServletListener implements ServletContextListener {

static final public String defFileName = "file.txt";
String fileName;

@Override
public void contextInitialized(ServletContextEvent sce) {
    List<Integer> lista=new LinkedList<Integer>();
    Random rand=new Random();
    int rozmiar=Integer.parseInt(sce.getServletContext().getInitParameter("rozmiar"));
    for(int i=0;i<rozmiar;i++){
        lista.add(rand.nextInt(100));
    }
    sce.getServletContext().setAttribute("lista", lista);

    fileName = sce.getServletContext().getInitParameter("SAVE_FILE");
    if (fileName == null) {
        fileName = defFileName;
    }
}

@Override
public void contextDestroyed(ServletContextEvent sce) {
//        throw new UnsupportedOperationException("Not supported yet.");
        List<Integer> lista=(List<Integer>) sce.getServletContext().getAttribute("lista");

    File file = new File(fileName);
    try (PrintWriter printWriter = new PrintWriter(file)) {
        for (Integer l:lista) {
            printWriter.println(l);
        }
    } catch (FileNotFoundException e) {
        throw new RuntimeException(e);
    }

}
}

这很奇怪，但文件无法创建。我应该添加到web吗。xml保存文件？或者我做错了什么。关闭重叠时应创建的文件

@WebListener public class SaveListener implements ServletContextListener { static final public String defFileName = "file.txt"; String fileName; @Override public void contextInitialized(ServletContextEvent sce) { // allow to find the name of the file in init parameters fileName = sce.getServletContext().getInitParameter("SAVE_FILE"); if (fileName == null) { fileName = defFileName; } } @Override public void contextDestroyed(ServletContextEvent sce) { List<String> lista = (List<String>) sce.getServletContext() .getAttribute("lista"); File file = new File(fileName); try (PrintWriter printWriter = new PrintWriter(file)) { for (String string : lista) { printWriter.println(string); } } catch (FileNotFoundException e) { throw new RuntimeException(e); } } }

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java如何将列表从servlet写入。文本

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