Java應用程序在Eclipse中正常運行，但不是.jar

Question

我正在創建一個使用iText創建4個PDF文件的Java應用程序。在創建帶有圖像的PDF文件的情況下，.jar會創建一個0字節的文件並且不會繼續執行。但是，當我右鍵單擊>>運行方式>> Java應用程序時，它工作得很好。要創建JAR，我做了以下

• 右鍵SRC
• 出口
• 運行的JAR文件
• 提取所需的庫到生成JAR
• 完成

而且文件「penguin.jpg」位於src目錄下。

這裏是我的代碼

import com.itextpdf.text.*; 
import com.itextpdf.text.pdf.PdfPTable; 
import com.itextpdf.text.pdf.PdfWriter; 
import java.io.FileOutputStream; 

public class ITextHelloWorld 
{ 
    public ITextHelloWorld() throws Exception 
    { 
     // Create the new document objects 
     Document helloWorld = new Document(); 
     Document bigHello = new Document(); 
     Document linux = new Document(); 
     Document tables = new Document(); 


    /********************************************************** 
         start Big Hello.pdf 
    This document is a huge document of text. Approximately 
    28 million characters, 24,391 pages, and 9.5 MB. 
    **********************************************************/ 
    PdfWriter.getInstance(bigHello, new FileOutputStream("Big Hello.pdf")); 
    bigHello.open(); 

    for (int i=0; i <1000000; i++) 
    { 
     bigHello.add(new Paragraph("Hello World. It's me again.")); 
    } 

    bigHello.close(); 
    /********************************************************** 
         end Big Hello.pdf 
    **********************************************************/ 

    /********************************************************** 
         start Tables.pdf 
    This document will have tables in it 
    **********************************************************/ 

    PdfWriter.getInstance(tables, new FileOutputStream("Tables.pdf")); 
    tables.open(); 

    PdfPTable table=new PdfPTable(4); 
    for (int i = 1; i<100; i++) 
    {  
     table.addCell("This is cell #" + i + ".\n"); 
    } 

    tables.add(table); 
    tables.close(); 
    /********************************************************** 
         end Tables.pdf 
    **********************************************************/ 

    /********************************************************** 
         start Linux.pdf 
    This is a document that has text, graphics, and links. 
    **********************************************************/ 
    PdfWriter.getInstance(linux, new FileOutputStream("Graphics and Text.pdf")); 
    linux.open();  
    Image image = Image.getInstance("penguin.jpg"); 
    linux.add(image); 

    linux.add(new Paragraph("Let's talk about Linux. \n\n" + 
      "Linux (commonly pronounced /ˈlɪnəks/ LIN-əks in American English, also pronounced " + 
      "/ˈlɪnʊks/ LIN-ooks in Europe and Canada) refers to the family of Unix-like computer " + 
      "operating systems using the Linux kernel. Linux can be installed on a wide variety of " + 
      "computer hardware, ranging from mobile phones, tablet computers and video game consoles, " + 
      "to mainframes and supercomputers. Linux is predominantly known for its use " + 
      "in servers; in 2009 it held a server market share ranging between 20–40%. Most desktop " + 
      "computers run either Microsoft Windows or Mac OS X, with Linux having anywhere from a " + 
      "low of an estimated 1–2% of the desktop market to a high of an estimated 4.8%. " + 
      "However, desktop use of Linux has become increasingly popular in recent years, partly " + 
      "owing to the popular Ubuntu, Fedora, Mint, and openSUSE distributions and the emergence" + 
      " of netbooks and smartphones running an embedded Linux.")); 

    linux.close(); 
    /********************************************************** 
         end Linux.pdf 
    **********************************************************/ 

    /********************************************************** 
         start Hello World.pdf 
    This document is one line of text. 
    **********************************************************/ 
    PdfWriter.getInstance(helloWorld, new FileOutputStream("Hello World.pdf")); 
    helloWorld.open(); 
    helloWorld.add(new Paragraph("Hello World. It's me again.")); 
    helloWorld.close(); 
    /********************************************************** 
         end Hello World.pdf 
    **********************************************************/ 

} 

public static void main (String args[]) 
{ 
    try 
    { 
     new ITextHelloWorld(); 
    } 

    catch (Exception e) 
    { 
     System.out.println(e); 
    } 
} 

}

感謝您的幫助！
Thomas

Answer 1

在猜測，問題就出在這行：

Image image = Image.getInstance("penguin.jpg"); 

由於這是在src目錄下，它會在JAR文件結束。但是，您不能直接從JAR文件加載文件，只使用文件名。

然而，Image.getInstance具有an overload，需要一個URL，這使得這個相當容易：

Image image = Image.getInstance(this.getClass().getResource("/penguin.jpg")); 

/是src目錄或jar文件（S），而不是文件系統根目錄的根目錄，如果你我想知道。

Answer 2

托馬斯，問題是當你創建jar時，你會搞亂目錄結構。您需要使用以下方法從jar中提取圖像：

InputStream stream = this.getClass().getClassLoader() 
           .getResourceAsStream("/images/image.jpg"); 

您應該根據需要編輯圖像的路徑。

你Image代碼會是這個樣子：

Image image = Image.getInstance(this.getClass().getResource("/penguin.jpg")); 

相關問題：

Java Swing Displaying Images From Within-a Jar

Answer 3

不知道你所得到的錯誤，我想這是一個CLASSPATH問題。當從命令行運行jar文件時，您需要傳遞classpath以指向相關的jar文件，或者系統classpath（環境變量）必須指向運行應用程序所需的所有jar文件。