如何在服务器端的GXT GWT中从本地计算机获取文件内容？(com.sencha.gxt.ui.GXT)

Question

我有GXT GWT项目(<inherits name='com.sencha.gxt.ui.GXT'/>)。我需要上传文件从计算机和获取字节数组的文件。

我在客户端写了上传文件，一切都很好，但是我需要添加服务器部分来获取文件的内容，怎么做呢？我的客户端：

public class FileUpload implements IsWidget {

    private static FileUploadUiBinder fileUploadUiBinder = GWT.create(FileUploadUiBinder.class);

    @UiTemplate("FileUpload.ui.xml")
    interface FileUploadUiBinder extends UiBinder<Component, FileUpload> {
    }

    @UiField
    FileUploadField uploadedFile;

    private FieldLabel label;

    @Override
    public Widget asWidget() {
        if (label == null) {
            label = (FieldLabel) fileUploadUiBinder.createAndBindUi(this);

            uploadedFile.addChangeHandler(new ChangeHandler() {
                @Override
                public void onChange(ChangeEvent event) {
                    Info.display("File Changed", "You selected " + uploadedFile.getValue());

                    }
                });
            }
            return label;
        }
    }

和FileUpload.ui.xml

        <!DOCTYPE ui:UiBinder SYSTEM "http://dl.google.com/gwt/DTD/xhtml.ent">
        <ui:UiBinder
                xmlns:form="urn:import:com.sencha.gxt.widget.core.client.form"
                xmlns:gxt="urn:import:com.sencha.gxt.widget.core.client"
                xmlns:ui='urn:ui:com.google.gwt.uibinder'
                xmlns="urn:import:com.sencha.gxt.widget.core.client.container"

                <form:FieldLabel>
                    <form:widget>
                        <form:FileUploadField ui:field="uploadedFile" name="metadataFile"/>
                    </form:widget>
                </form:FieldLabel>

        </ui:UiBinder>

所以:我需要添加服务器部分:如何在服务器部分中获取字节数组(文件内容)？我需要一个例子:)也许有人给我提供了工作例子的链接？请帮帮我。

Answer 1

不幸的是，为了展示一些如何将文件数据发送到服务器端的示例，您的代码需要做很多更改。我应该提一下，这只是一种可能的解决方案。不过，这里的客户机-服务器请求将发送到HttpServlet，而不是通过标准的GWT RPC。以下是我的更改：

1)更改FileUpload.ui.xml：

<!DOCTYPE ui:UiBinder SYSTEM "http://dl.google.com/gwt/DTD/xhtml.ent">
<ui:UiBinder xmlns:form="urn:import:com.sencha.gxt.widget.core.client.form"
    xmlns:gxt="urn:import:com.sencha.gxt.widget.core.client"
    xmlns:ui='urn:ui:com.google.gwt.uibinder'
    xmlns="urn:import:com.sencha.gxt.widget.core.client.container"
>
    <form:FormPanel>
        <form:FieldLabel>
            <form:widget>
                <form:FileUploadField ui:field="uploadedFile"
                    name="metadataFile" />
            </form:widget>
        </form:FieldLabel>
    </form:FormPanel>
</ui:UiBinder>

2)更改FileUpload.java：

import com.google.gwt.core.client.GWT;
import com.google.gwt.event.dom.client.ChangeEvent;
import com.google.gwt.event.dom.client.ChangeHandler;
import com.google.gwt.uibinder.client.UiBinder;
import com.google.gwt.uibinder.client.UiField;
import com.google.gwt.uibinder.client.UiTemplate;
import com.google.gwt.user.client.ui.IsWidget;
import com.google.gwt.user.client.ui.Widget;
import com.sencha.gxt.widget.core.client.Component;
import com.sencha.gxt.widget.core.client.event.SubmitCompleteEvent;
import com.sencha.gxt.widget.core.client.form.FileUploadField;
import com.sencha.gxt.widget.core.client.form.FormPanel;
import com.sencha.gxt.widget.core.client.info.Info;

public class FileUpload implements IsWidget {

    private static FileUploadUiBinder fileUploadUiBinder = GWT.create(FileUploadUiBinder.class);

    @UiTemplate("FileUpload.ui.xml")
    interface FileUploadUiBinder extends UiBinder<Component, FileUpload> {
    }


    @UiField
    FileUploadField uploadedFile;

    private FormPanel formPanel;

    @Override
    public Widget asWidget() {
        if (formPanel == null) {
            formPanel = (FormPanel) fileUploadUiBinder.createAndBindUi(this);

            formPanel.setEncoding(FormPanel.Encoding.MULTIPART);
            formPanel.setMethod(FormPanel.Method.POST);
            formPanel.setAction("file.upload");  // This action should
            // point to servlet registered in WEB_INF/web.xml
            formPanel.addSubmitCompleteHandler(new SubmitCompleteEvent.SubmitCompleteHandler() {
                public void onSubmitComplete(SubmitCompleteEvent event) {
                    String resultHtml = event.getResults();
                    Info.display("Upload Response", resultHtml);
                }
            });

            uploadedFile.addChangeHandler(new ChangeHandler() {
                @Override
                public void onChange(ChangeEvent event) {
                    Info.display("File Changed", "You selected " + 
                            uploadedFile.getValue());
                    formPanel.submit();  // It's better to do it by 
                    // clicking on submitting button or something. 
                }
            });
        }
        return formPanel;
    }
}

3) web.xml (只添加parts，不使用home.test.uploadtest，使用自己的包)：

<... other servlet blocks ...>
<servlet>
    <servlet-name>fileUploadServlet</servlet-name>
    <servlet-class>home.test.uploadtest.server.FileUploadServlet</servlet-class>
</servlet>   

<... other servlet-mapping blocks ...>
<servlet-mapping>
    <servlet-name>fileUploadServlet</servlet-name>
    <url-pattern>/file.upload</url-pattern>
</servlet-mapping> 

4) FileUploadServlet.java (主要是服务器端操作的虚拟示例)：

import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class FileUploadServlet extends HttpServlet {
    private static final long serialVersionUID = -1L;

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/plain");
        File tempDir = new File(System.getProperty("java.io.tmpdir"));
        FileItemFactory factory = new DiskFileItemFactory(1000000, tempDir);
        ServletFileUpload upload = new ServletFileUpload(factory);
        File target = null;
        try {
            try {
                List<?> items = upload.parseRequest(request);
                Iterator<?> it = items.iterator();
                while (it.hasNext()) {
                    FileItem item = (FileItem) it.next();
                    if (item.isFormField()) {
                        throw new ServletException("Unsupported non-file property [" + 
                                item.getFieldName() + "] with value: " + item.getString());
                    } else {
                        target = File.createTempFile("temp_", ".data", tempDir);
                        item.write(target);
                        item.delete();
                        System.out.println("Temp file: " + target.getAbsolutePath());
                    }
                }
            } catch (ServletException e) {
                throw e;
            } catch (Exception e) {
                throw new IllegalStateException(e);
            }
            response.getWriter().write("File length: " + target.length());
            response.getWriter().close();
        } finally {
            if (target != null && target.exists())
                target.delete();
        }
    }   
}

因此，正如您所看到的，存在对https://commons.apache.org/proper/commons-fileupload/的依赖

PS:我认为由于代码太多，我可能会忘记一些东西。在这种情况下，请让我知道。