Gradle构建Java Web应用：Servlet依赖与Tomcat插件(转)

轻轻的

　　Gradle的官方tutorial介绍了构建Java Web应用的基本方法。不过在使用Servlet做上传的时候会碰到问题。这里分享下如何通过Servlet上传文件，以及如何使用Gradle来构建相应的Java Web工程。
　　参考原文：How to Build Web Scanning Application with Gradle

Servlet文件上传
　　使用Servlet文件上传，可以参考Oracle的官方文档The fileupload Example Application。这里需要注意的一个问题就是要接收multipart/form-data数据，在Servlet中必须申明：



@WebServlet(name = "FileUploadServlet", urlPatterns = {"/upload"})
@MultipartConfig
　　不然，getPart()会返回空。Servlet接收上传文件可以这样写：



/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package com.dynamsoft.upload;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
@WebServlet(name = "DWTUpload", urlPatterns = {"/DWTUpload"})
@MultipartConfig
public class DWTUpload extends HttpServlet {
    private final static Logger LOGGER =
            Logger.getLogger(DWTUpload.class.getCanonicalName());
    /**
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
     * methods.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request,
        HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    // Create path components to save the file
    final Part filePart = request.getPart("RemoteFile");
    final String fileName = getFileName(filePart);
    OutputStream out = null;
    InputStream filecontent = null;
    final PrintWriter writer = response.getWriter();
    String realPath = getServletContext().getRealPath("/");
    if (realPath == null)
        realPath = "f:\\web_upload"; // modify the default uploading dir accordingly
    String uploadPath = realPath + File.separator + "upload";
    File uploadDir = new File(uploadPath);
    if (!uploadDir.exists())
        uploadDir.mkdir();
    try {
        out = new FileOutputStream(new File(uploadPath + File.separator
                + fileName));
        filecontent = filePart.getInputStream();
        int read = 0;
        final byte[] bytes = new byte[1024];
        while ((read = filecontent.read(bytes)) != -1) {
            out.write(bytes, 0, read);
        }
        writer.println("New file " + fileName + " created at " + uploadPath);
        LOGGER.log(Level.INFO, "File{0}being uploaded to {1}",
                new Object[]{fileName, uploadPath});
    } catch (FileNotFoundException fne) {
        writer.println("You either did not specify a file to upload or are "
                + "trying to upload a file to a protected or nonexistent "
                + "location.");
        writer.println("<br/> ERROR: " + fne.getMessage());
        LOGGER.log(Level.SEVERE, "Problems during file upload. Error: {0}",
                new Object[]{fne.getMessage()});
    } finally {
        if (out != null) {
            out.close();
        }
        if (filecontent != null) {
            filecontent.close();
        }
        if (writer != null) {
            writer.close();
        }
    }
}
private String getFileName(final Part part) {
    final String partHeader = part.getHeader("content-disposition");
    LOGGER.log(Level.INFO, "Part Header = {0}", partHeader);
    for (String content : part.getHeader("content-disposition").split(";")) {
        if (content.trim().startsWith("filename")) {
            return content.substring(
                    content.indexOf('=') + 1).trim().replace("\"", "");
        }
    }
    return null;
}
    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }
    /**
     * Handles the HTTP <code>POST</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }
    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>
}
Gradle构建Java Web工程
　　在使用Gradle构建这个Web工程的时候，如果按照官方文档，getPart这个方法是找不到的，用到的依赖可以换成：



dependencies {
   providedCompile "javax:javaee-api:6.0"
}
　　另外一个问题就是使用jetty插件了，同样会失败。因为jetty不支持Servlet 3.0。官方论坛里有回复： Unable to use servlet 3.0 api in jetty plugin。替代方法可以使用Gradle Tomcat plugin 。在build.gradle文件中添加：



buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.bmuschko:gradle-tomcat-plugin:2.1'
    }
}
subprojects {
   apply plugin : "java"
   repositories {
      mavenCentral()
   }
}
　　然后在子工程的build.gradle文件中添加tomcat插件：



apply plugin: "war"
apply plugin: 'com.bmuschko.tomcat'
dependencies {
   providedCompile "javax:javaee-api:6.0"
   def tomcatVersion = '7.0.59'
   tomcat "org.apache.tomcat.embed:tomcat-embed-core:${tomcatVersion}",
    "org.apache.tomcat.embed:tomcat-embed-logging-juli:${tomcatVersion}",
      "org.apache.tomcat.embed:tomcat-embed-jasper:${tomcatVersion}"
}
tomcat {
    httpPort = 8080
    httpsPort = 8091
    enableSSL = true
}
　　最后构建运行工程：



gradle build
gradle tomcatRunWar

源码
　　https://github.com/Dynamsoft/Dynamic-Web-TWAIN/tree/master/samples/gradle

git clone https://github.com/Dynamsoft/Dynamic-Web-TWAIN.git


原文地址：http://www.codepool.biz/gradle/how-to-build-web-scanning-application-with-gradle.html　　http://my.oschina.net/yushulx/blog/401888