servlet路径问题

Question

代码一：

package com.main.service;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import java.io.PrintWriter;


public class ReadData {
    
         public static void main(String[] args) {
                 try {
                     testSaxReader("person");
                     System.out.println("---------");
                     testSaxReader("隶属度");
                 } catch (Exception e) {
                     e.printStackTrace();
                 }
                 
             }
              public static void testSaxReader(String item) throws DocumentException, FileNotFoundException {
                  SAXReader saxReader = new SAXReader();
                  System.out.println("工程路径："+System.getProperty("user.dir"));//问题所在
                  FileInputStream file = new FileInputStream("src/0625.xml");
                  Document doc = saxReader.read(file);
                  Element menu = doc.getRootElement();
                  System.out.println(menu.getName());
                  org.dom4j.Node person=menu.selectSingleNode("/Menu//Item[@Title='"+item+"']");
                  String nodeValue = person.getText();
                  System.out.println(nodeValue);
                  File fp=new File("./data/"+item+".txt");
                  PrintWriter pfp= new PrintWriter(fp);
                  pfp.print(nodeValue);
                  pfp.close();
                  
              }
    
}

代码一有main方法,System.out.println("工程路径："+System.getProperty("user.dir"));打印出来的结果是工程路径：E:\workspace\outer\javaConnectR，是我项目的路径。

代码二：

package com.main.service;


import java.awt.Graphics;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.HeadlessException;
import java.awt.Image;
import java.awt.MediaTracker;
import java.awt.Toolkit;
import java.awt.Transparency;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;


import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;

import org.rosuda.REngine.REXP;
import org.rosuda.REngine.Rserve.RConnection;

import com.main.util.Rservel;

public class Execute extends JFrame{
private static final long serialVersionUID=1L;
static Image img;
public REXP getRobj() throws Exception{
    System.out.println("getRobj()");
    
    RConnection c=Rservel.getRConnection();
    c.eval("library(RColorBrewer)");
    c.eval("H <- c(7,12,28,3,41)");
    c.eval("colors<-brewer.pal(5,'Set1')");
    c.parseAndEval(" barplot(H,rep(1,5),col=colors);dev.off()");
    xp=c.parseAndEval("r=readBin('test.jpg','raw',3000*3000);unlink('test.jpg');r");
    return xp;
}
    
    
    public void createPlot(REXP xp, JFrame f,String path)throws Exception{
        
        try {
            Image image=Toolkit.getDefaultToolkit().createImage(xp.asBytes());
            BufferedImage bufferedImage=toBufferedImage(image);
            System.out.println("工程路径："+System.getProperty("user.dir"));
           ImageIO.write(bufferedImage, "JPG", new File(path+"/outImg/98.jpg"));//
          
       } catch (IOException e) {
           e.printStackTrace();
       }
    }

    public  BufferedImage toBufferedImage(Image image) {  
        if (image instanceof BufferedImage) {  
            return (BufferedImage)image;  
         }  
         image = new ImageIcon(image).getImage();  
         BufferedImage bimage = null;  
         GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();  
        try {  
             
            int transparency = Transparency.OPAQUE;   
             GraphicsDevice gs = ge.getDefaultScreenDevice();  
             GraphicsConfiguration gc = gs.getDefaultConfiguration();  
             bimage = gc.createCompatibleImage(  
             image.getWidth(null), image.getHeight(null), transparency);  
         } catch (HeadlessException e) {  
         }  
        
        if (bimage == null) {   
            int type = BufferedImage.TYPE_INT_RGB;   
             bimage = new BufferedImage(image.getWidth(null), image.getHeight(null), type);  
         }  
         Graphics g = bimage.createGraphics();  
         g.drawImage(image, 0, 0, null);  
         g.dispose();  
        
        return bimage;  
    } 

}


 

package com.main.web;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.rosuda.REngine.REXP;
import org.rosuda.REngine.Rserve.RConnection;
import org.rosuda.REngine.Rserve.RserveException;

import com.main.service.Execute;

/**
 * Servlet implementation class ExecuteR
 */
@WebServlet("/ExecuteR")
public class ExecuteR extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ExecuteR() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String RSentences=request.getParameter("data");//这个例子必须到页面点击
        //System.out.println(filePath);
        String path=getServletContext().getRealPath("/");
        System.out.println("servlet路径："+path);
        Execute wc=new Execute();
        REXP xp;
        try {
            xp = wc.getRobj();
            wc.createPlot(xp,wc,path)
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

代码二：没有main方法，是一个java类，通过servlet调用，System.out.println("工程路径："+System.getProperty("user.dir"));打印出来结果是工程路径:E:\BE\eclipse\eclipse，是我安装eclipse的路径，不是项目路径；代码String path=getServletContext().getRealPath("/");打印出来结果是：servlet路径：E:\workspace\eclipse_jee_mars2\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\javaConnectR\

1.请问为什么会有这样的区别？？
2.我希望代码二里的ImageIO.write(bufferedImage, "JPG", new File(path+"/outImg/98.jpg"));new File里的路径是和代码一System.getProperty("user.dir"));打印出来的路径E:\workspace\outer\javaConnectR一致，为项目路径。请问该怎么解决？？

Answer 1

1. user.dir 指向的是你启动 JVM 的地方，你可以看看这里

代码一是你从工程路径下启动的，但是代码二你的 Servlet 是被容器 (Tomcat等等)加载进 JVM 的，而此时 user.dir 指的是这些容器的路径，这方面你需要了解一下容器是怎样运行的。

1. 你要分清楚：开发环境、上线环境。

你在 E:\workspace\outer\javaConnectR 写代码，这是开发环境，但是当你打包成 .war 时，它会被容器解压到一个目录，比如你代码二中输出的 E:\workspace\...\wtpwebapps\javaConnectR\，此时它无论如何也不可能按你所想去读到开发时的路径，因为代码二实际运行的时候文件已经不在你开发的路径上了。

Answer 2

我就用通俗的话来说一下吧：

1. System.out.println("工程路径："+System.getProperty("user.dir"));这段代码由JVM执行，因此输出的是类路径，getServletContext().getRealPath("/");是由Tomcat执行，在Eclipse下配置Tomcat，Tomcat会将代码默认输出到另外的文件夹中(当然了，该路径是可以配置的)。

它俩输出的结果不同主要是因为执行的主体不一致，JVM和Tocmat

1. 你想要的是将图片输出到项目路径对吧？可以在配置文件中配置，然后读取就行啦。写个properties,devProjectPath=http://localhost:8080/xxx,devProjectPath=http://localhost:8080/xxx，productionProjectPath=http://www.xxxx.com

水平有限，如果有错的地方请指出