Java应用程序在Eclipse中正常运行，但不是以.jar的形式运行

Question

我正在创建一个使用iText创建4个PDF文件的Java应用程序。在创建包含图像的PDF文件时，.jar将创建一个0字节文件，并且不会继续执行。但是，当我正确地将>>运行为>>时，它工作得很好。要创建jar，我将执行以下操作

• 右击src
• 导出
• 可运行JAR文件
• 将所需库提取到生成的JAR中
• 完成

文件"penguin.jpg“位于src目录下。

这是我的密码

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);
    }
}

}

谢谢你的帮助！

托马斯

Answer 1

据猜测，问题就在于这一行：

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

因为这是在src目录中，所以它将在JAR文件中结束。但是，不能直接用文件名从JAR文件中加载文件。

然而，Image.getInstance有一个采用URL的过载，这使得这非常容易：

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

/是src目录或jar文件的根，而不是文件系统根，以防您有疑问。

Answer 2

Thomas，问题是，当您创建jar时，您会“搞乱”目录结构。您需要使用以下方法从jar中提取图像：

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

您应该根据需要编辑图像的路径。

您的Image代码如下所示：

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

有关问题：

Java Swing从内部显示图像-一个Jar

Answer 3

在不知道所得到的错误的情况下，我猜这是CLASSPATH问题。当您从命令行运行jar文件时，您需要传递类路径来指向依赖的jar文件，或者系统类路径(环境变量)必须指向运行应用程序所需的所有jar文件。