jsp 起航 和Servlet通过attribute通信

@WebServlet(name = "ticketServlet",urlPatterns = {"/tickets"},loadOnStartup = 1)
@MultipartConfig(fileSizeThreshold = 5242880,
maxFileSize = 20971520L,//20MB
maxRequestSize = 41943040L//40MB
)
public class TicketServlet extends HttpServlet{
    //线程可见性
    private volatile int TICKET_ID_SEQUENCE = 1;
    private Map<Integer,Ticket> ticketDatabase = new LinkedHashMap<>();

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {

        //使用请求参数做了一个菜单
        String action = req.getParameter("action");
        if (action == null){
            action = "list";//默认ticket列表
        }
        switch (action){
            case "create":
                this.showTicketForm(req,resp);//展示表单
                break;
            case "view":
                this.viewTicket(req,resp);//具体一张
                break;
            case  "download":
                this.downloadAttachment(req,resp);//下载附件
                break;
            default:
                this.listTickets(req,resp);//展示ticket
                break;
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        String action = req.getParameter("action");
        if(action == null){
            action = "list";
        }
        switch (action){
            case "create":
                this.createTicket(req,resp);//表单提交实际创建方法
                break;
            case "list":
            default:
                resp.sendRedirect("tickets");//重定向 get
                break;

        }

    }


    private void listTickets(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException {
        request.setAttribute("ticketDatabase",this.ticketDatabase);
        request.getRequestDispatcher("/WEB-INF/jsp/view/listTickets.jsp").forward(request,response);
    }

    private void viewTicket(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
        //从ticket列表进入某张ticket所需要id
        String idString = request.getParameter("ticketId");
        Ticket ticket = this.getTicket(idString, response);
        if(ticket == null)
            return;
        request.setAttribute("ticketId",idString);
        request.setAttribute("ticket",ticket);

        request.getRequestDispatcher("/WEB-INF/jsp/view/viewTicket.jsp")
                .forward(request,response);
    }

    private Ticket getTicket(String id, HttpServletResponse response) throws IOException {
        //id.len == ''  一般合法性检查  有没有
        if (id == null || id.length()==0){
            response.sendRedirect("tickets");
            return null;
        }
        try {
            //parse异常
            Ticket ticket = this.ticketDatabase.get(Integer.parseInt(id));
            //都考虑失败 没有的情况
            if (ticket == null) {
                response.sendRedirect("tickets");
                return null;
            }
            return ticket;
        }catch (Exception e){
            response.sendRedirect("tickets");
            return null;
        }
    }

    private void showTicketForm(HttpServletRequest req,HttpServletResponse resp) throws IOException, ServletException {
//        内部转发，而不是重定向，用户浏览器不会收到重定向状态码，浏览器URL也不改变
//        内部请求处理转发至应用程序不同部分，forward后，Servlet代码没有控制权再操作响应对象。
        req.getRequestDispatcher("/WEB-INF/jsp/view/ticketForm.jsp").forward(req,resp);
    }


    private void downloadAttachment(HttpServletRequest request, HttpServletResponse response) throws IOException {
       //下载某一个attachment
        String idString = request.getParameter("ticketId");
        Ticket ticket = this.getTicket(idString, response);
        if(ticket == null)
            return;

        String name = request.getParameter("attachment");
        if(name == null)
        {
            response.sendRedirect("tickets?action=view&ticketId=" + idString);
            return;
        }

        Attachment attachment = ticket.getAttachment(name);
        if(attachment == null)
        {
            response.sendRedirect("tickets?action=view&ticketId=" + idString);
            return;
        }
        //header 内容位置   文件名
        response.setHeader("Content-Disposition",
                "attachment; filename=" +
                        new String(attachment.getName().getBytes("UTF-8"),"ISO8859-1"));

        response.setContentType("application/octet-stream");
        //流
        ServletOutputStream stream = response.getOutputStream();
        stream.write(attachment.getContents());
    }


    private void createTicket(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
        Ticket ticket = new Ticket();
        ticket.setCustomerName(req.getParameter("customerName"));
        ticket.setSubject(req.getParameter("subject"));
        ticket.setBody(req.getParameter("body"));

        Part filePart = req.getPart("file1");
        if (filePart!=null){
            Attachment attachment = this.processAttachment(filePart);
            if (attachment!=null)
                ticket.addAttachment(attachment);
        }
        int id;
        synchronized (this){
            id = this.TICKET_ID_SEQUENCE++;
            this.ticketDatabase.put(id,ticket);
        }
        resp.sendRedirect("tickets?action=view&ticketId="+id);
    }

    private Attachment processAttachment(Part filePart) throws IOException {
        InputStream inputStream = filePart.getInputStream();//用户输入流
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();//写入attachment做准备

        int read;
        final byte[] bytes  = new byte[1024];//buffer
        while((read=inputStream.read(bytes))!=-1){//有多少
            outputStream.write(bytes,0,read);//写多少
        }

        Attachment attachment = new Attachment();
        attachment.setName(filePart.getSubmittedFileName());
        attachment.setContents(outputStream.toByteArray());

        return attachment;
    }

【展示ticket表单】

<%--<%@ page contentType="text/htmlcharset=UTF-8" %>--%>
<%@ page session="false" %>
<html>
<head>
    <title>Create a Ticket</title>
</head>
<body>
    <%--//编码类型multipart/form-data--%>
<form method="POST" action="tickets" enctype="multipart/form-data">
    <%--//隐藏域提交 action value = create--%>
    <input type="hidden" name="action" value="create"/>
    Your Name<br/>
    <input type="text" name="customerName"/><br/><br/>
    Subject<br/>
    <input type="text" name="subject"/><br/><br/>
    Body<br/>
    <textarea name="body" rows="5" cols="30"></textarea><br/><br/>
    <b>Attachments</b><br/>
    <input type="file" name="file1"/><br/><br/>
    <input type="submit" value="提交"/>
</form>
</body>
</html>

【查看Ticket】

<%@ page import="net.mypla.model.Ticket" %>
<%@ page session="false" %>
<%
    String ticketId = (String) request.getAttribute("ticketId");
    Ticket ticket = (Ticket) request.getAttribute("ticket");
%>
<html>
<head>
    <title>客户支持系统</title>
</head>
<body>
    <h2>Ticket #<%= ticketId%>: <%=ticket.getSubject()%></h2>
    <i>Customer Name - <%= ticket.getCustomerName()%></i><br /><br />
    <%= ticket.getBody()%><br /><br />
    <%
        if(ticket.getNumberOfAttachments()>0){
            %>Attachments:<%
            int i = 0;
            for(Attachment a:ticket.getAttachments()){
                if(i++>0)
                    out.print(",");
                %><a href="<c:url value="/tickets">
                    <c:param name="action" value="download"/>
                    <c:param name="ticketId" value="<%= ticketId%>"/>
                    <c:param name="attachment" value="<%= a.getName()%>"/>
                </c:url>"><%= a.getName()%></a><%
            }
        }
    %><br/>
    <a href="<c:url value="/tickets" />">Return to list tickets</a>
</body>
</html>

【查看tickets列表】

<%@ page session="false" import="java.util.Map" %>
<%@ page import="net.mypla.model.Ticket" %>
<%
    @SuppressWarnings("unchecked")
    Map<Integer,Ticket> ticketDatabase = (Map<Integer, Ticket>) request.getAttribute("ticketDatabase");
%>
<html>
<head>
    <title>消费者支持系统</title>
</head>
<body>
    <h2>Tickets</h2>
    
    <a href="<c:url value="/tickets"><c:param name="action" value="create"/></c:url>">Create Ticket</a><br/><br/>
    <%
        if(ticketDatabase.size() == 0){
            %><i>There are no tickets in the system.</i><%
        }
        else{
            for(int id : ticketDatabase.keySet()){
                String idString = Integer.toString(id);
                Ticket ticket = ticketDatabase.get(id);
                %>Ticket #<%= idString%>:<a href="<c:url value="/tickets">
                    <c:param name="action" value="view"/>
                    <c:param name="ticketId" value="<%= idString%>"/></c:url>"><%= ticket.getSubject()%></a>
        ( customer:<%= ticket.getCustomerName() %>)<br /><%
        }
}
%>
</body>
</html>

 

【部署描述符】

<jsp-config>
    <jsp-property-group>
        <url-pattern>*.jsp</url-pattern>
        <url-pattern>*.jspf</url-pattern>
        <page-encoding>UTF-8</page-encoding>
        <scripting-invalid>false</scripting-invalid>
        <include-prelude>/WEB-INF/jsp/base.jspf</include-prelude>
        <!--jsp转换器删除响应输出中空白，只留指令、声明、脚本、jsp标签-->
        <trim-directive-whitespaces>true</trim-directive-whitespaces>
        <default-content-type>text/html</default-content-type>
    </jsp-property-group>
</jsp-config>