java将一个文件从JSP发送到调用接口方法的控制器。如何从该请求上载文件？
大家好，我正在做一个项目
希望你能帮助我解决我的问题。。我挣扎了5天
在分配给我的模块中，我必须将文件、标题、类别、UploadedByDetails从JSP上传到控制器。它将request和responce存储在名为execute()的方法中，该方法存在于Command.java接口中
现在，当我传递所有上传表单详细信息时，它会一直传递到名为ResourceCommand.java implements Command的类，该类调用DAO并在中间停止执行
上传的部分代码。jsp
<form name="myform_up" method="post" action = "Controller">
<input type="hidden" name="form_action" value="resource" />
<input type="hidden" name="action" value="insert" />
<table>
<tr>
<td>Document Title <font color="red">*</font></td></tr>
<tr>
<td><input type="text" name="name" /></td></tr>
<tr>
<td>Category <font color="red">*</font>
<select name="cat">
<option value="Java" selected >Java Material</option>
<option value="Net">.Net Material</option>
<option value="C">C and C# Material</option>
</select></td>
</tr>
<input type="hidden" name="uploadedby" value="<jsp:getProperty name="userBean" property="user" />" />
<tr>
<td>Upload A file:
<input type="file" name="file1"/></td>
</tr>
<tr>
<td><br/><input type="checkbox" name="t_condition" checked />I Had received Copyrights for this Document</td>
</tr>
<TR>
<td ALIGN="CENTER"><br/>
<INPUT class="button blue" TYPE="submit" value="Upload" />
<INPUT class="button red" TYPE="reset" value="Clear" />
</td></TR>
</TABLE>
</FORM>
来自控制器的部分代码。java
public void init(ServletConfig config) throws ServletException{
super.init();
System.out.println("i am in init");
this.commands.put("login", new LoginCommand());
this.commands.put("resource", new ResourceCommand());
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("i am in doget");
processCommand(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("i am in dopost");
processCommand(request, response);
}
private void processCommand(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String formAction = request.getParameter("form_action");
System.out.println("implementing formAction = " + formAction);
Commands command = (Commands) commands.get(formAction);
command.execute(request, response);
}
}
ResourceCommand中的部分代码。java
public class ResourceCommand extends HttpServlet implements Commands{
private static final long serialVersionUID = 1L;
public void execute(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
if ("insert".equalsIgnoreCase(request.getParameter("action"))) {
this.addResource(request, response);
}
}
private void addResource(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException{
ResourceBean ResourceBean = new ResourceBean();
mapToResourceBeans(request, ResourceBean);
String result = null;
try {
result = new ResourceDAO().uploadResource(request, ResourceBean);
} catch (Exception ex) {
System.err.println(" Error in inserting new resource");
}
if ("success".equalsIgnoreCase(result)) {
// if Block CODE
}
else {
//Else block CODE
}
}
private void mapToResourceBeans(HttpServletRequest request,
ResourceBean ResourceBean) {
ResourceBean.setName(request.getParameter("name"));
ResourceBean.setCat(request.getParameter("cat"));
ResourceBean.setUploadedby(request.getParameter("uploadedby"));
}
}
命令中的部分代码。java
public interface Commands {
public void execute(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException;
}
ResourceDAO中的部分代码。java
public class ResourceDAO {
static final String SUCCESS = "success";
static final String FAILURE = "failure";
static Logger log = Logger.getLogger("com.a");
public String uploadResource(HttpServletRequest request,
ResourceBean newResource) throws FileNotFoundException {
String result = null;
PreparedStatement stmtInsert = null;
// Create a Database Connection
Connection con = ConnectionDAO.getJDBCConnection();
try {
PreparedStatement pstmt = con
.prepareStatement("INSERT INTO resource(name, cat, uploadedby, file) values(?,?,?,?)");
pstmt.setString(1, newResource.getName());
System.out.println(newResource.getName());
pstmt.setString(2, newResource.getCat());
System.out.println(newResource.getCat());
pstmt.setString(3, newResource.getUploadedby());
System.out.println(newResource.getUploadedby());
String file = request.getParameter("file1");
System.out.println("0");
File f = new File(file);
System.out.println("1");
FileInputStream fis = new FileInputStream(f);
System.out.println("2");
pstmt.setBinaryStream(4, fis, (int) f.length());
System.out.println("3");
int rows = pstmt.executeUpdate();
result = SUCCESS;
if (rows != 1) { result = FAILURE; }
} catch (SQLException ex) {
result = FAILURE;
ConnectionDAO.rollbackJDBCConnection(con);
ex.printStackTrace();
} finally {
ConnectionDAO.commitJDBCConnection(con);
ConnectionDAO.closeStatement(stmtInsert);
ConnectionDAO.closeJDBCConnection(con);
}
return result;
}
}
控制台显示器
implementing formAction = resource
Error in inserting new resource
123
Net
null
0
1
i am going back to addResource page
如果我在表单标记中放置enctype="multipart/form-data"。。那我就买这个
java.lang.NullPointerException
com.kbcss.controller.Controller.processCommand(Controller.java:57)
com.kbcss.controller.Controller.doPost(Controller.java:49)
javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
我完全迷路了。。Plz帮助
# 1 楼答案
这是56号线吗？错误之前的那个
如果在
commands映射（您没有显示）中找不到该命令，则它可能返回null。您至少应该检查映射返回的命令是否有效当找不到匹配的内容时，
Map将返回null。在下一行中，您使用它并将得到一个NullPointerException# 2 楼答案
我发现我应该使用Serlvet 3.0使事情正常进行。。 我感谢大家为我的代码付出了一些努力：p