一、問題
當開啟 minimizeJar 后，精簡的Jar運行會出現如下錯誤：
The image could not be loaded: FileImageDescriptor(location=class org.eclipse.jface.dialogs.TitleAreaDialog, name=images/title_banner.png)
org.eclipse.jface.resource.DeviceResourceException: Unable to create resource FileImageDescriptor(location=class org.eclipse.jface.dialogs.TitleAreaDialog, name=images/title_banner.png)
at org.eclipse.jface.resource.ImageDescriptor.createResource(ImageDescriptor.java:184)
at org.eclipse.jface.resource.DeviceResourceManager.allocate(DeviceResourceManager.java:55)
at org.eclipse.jface.resource.AbstractResourceManager.create(AbstractResourceManager.java:88)
at org.eclipse.jface.resource.ResourceManager.createImageWithDefault(ResourceManager.java:195)
…………
出現這個錯誤的直接現象是所有的圖片——包括圖標——都無法正確顯示。
二、分析
開始以為是resources打包錯誤導致沒有被壓進jar包，不過分析jar包內容發現并沒有文件缺失，然后開始分析minimizeJar的機制。文檔上說：
<minimizeJar>
When true, dependencies will be stripped down on the class level to only the transitive hull required for the artifact. Note: Usage of this feature requires Java 1.5 or higher.
由此來看，shade做的只是做了靜態調用分析，并沒有做動態類加載運行分析，因此極大可能問題是出在這里了。而且從拋出的異常來看，有可能是圖片文件格式無法解析導致了圖片資源創建失敗。
那么之后的調試方法就簡單了，首先上verbose大法，直接加verbose:class參數，分別運行正常的和異常的Jar包，從輸出信息發現了端倪：
[Loaded java.lang.IndexOutOfBoundsException from C:\Program Files\Java\jre1.8.0_151\lib\rt.jar]
[Loaded java.lang.ArrayIndexOutOfBoundsException from C:\Program Files\Java\jre1.8.0_151\lib\rt.jar]
[Loaded org.eclipse.swt.internal.image.WinBMPFileFormat from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.GIFFileFormat from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.WinICOFileFormat from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.JPEGFileFormat from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.JPEGSegment from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.JPEGFixedSizeSegment from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.JPEGStartOfImage from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.PNGFileFormat from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.PngInputStream from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.PngDecodingDataStream from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.PngChunkReader from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.PngChunk from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.PngIhdrChunk from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.PngFileReadState from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.PngPlteChunk from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.PngIdatChunk from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.PngIendChunk from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.image.PngTrnsChunk from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.win32.BITMAPINFOHEADER from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.jface.window.ToolTip$ToolTipOwnerControlListener from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.jface.window.ToolTip$$Lambda$19/1873653341 from org.eclipse.jface.window.ToolTip]
[Loaded org.cncert.xac.utils.ResourceManager from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.widgets.ToolItem from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.internal.win32.TBBUTTON from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.jface.resource.AbstractResourceManager$RefCount from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.layout.FormData from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.swt.layout.FormAttachment from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.jface.dialogs.TitleAreaDialog$1 from file:/E:/Temp/*****.jar]
[Loaded org.eclipse.jface.window.ToolTip$TooltipHideListener from file:/E:/Temp/*****.jar]
注意上方紅色的字體，在異常的Jar包輸出中是沒有的，同時檢查了Jar包中果然沒有打包這幾個類！將這幾個類手動加入Jar包后，異常的Jar包可以正常運行了。
從源代碼看，這幾個類型是SWT在運行時動態加載的，由 org.eclipse.swt.internal.image.FileFormat 動態加載，相關代碼如下：
package org.eclipse.swt.internal.image;
import java.io.*;
import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
/**
* Abstract factory class for loading/unloading images from files or streams
* in various image file formats.
*
*/
public abstract class FileFormat {
static final String FORMAT_PACKAGE = "org.eclipse.swt.internal.image"; //$NON-NLS-1$
static final String FORMAT_SUFFIX = "FileFormat"; //$NON-NLS-1$
static final String[] FORMATS = {"WinBMP", "WinBMP", "GIF", "WinICO", "JPEG", "PNG", "TIFF", "OS2BMP"}; //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$//$NON-NLS-5$ //$NON-NLS-6$//$NON-NLS-7$//$NON-NLS-8$
LEDataInputStream inputStream;
LEDataOutputStream outputStream;
ImageLoader loader;
int compression;
static FileFormat getFileFormat (LEDataInputStream stream, String format) throws Exception {
Class<?> clazz = Class.forName(FORMAT_PACKAGE + '.' + format + FORMAT_SUFFIX);
FileFormat fileFormat = (FileFormat) clazz.getDeclaredConstructor().newInstance();
if (fileFormat.isFileFormat(stream)) return fileFormat;
return null;
}
三、Maven配置的修改
在官方文檔中，可以使用filter來顯式包含不想被minimizeJar優化掉的內容，但是目前filter還無法做到針對一個artifact中選擇性對某個目錄下的文件不做優化。
例如，我希望shade不對org/eclipse/swt/internal/image/**做優化，我的配置是這樣的：
<filter>
<artifact>org.eclipse:swt.win32.x86_64</artifact>
<includes>
<include>org/eclipse/swt/internal/image/**</include>
</includes>
</filter>
但最終的結果是只打包了這個目錄內的類，而這個artifact中的其他類全部被removed，因為
官方demo中有這樣一句話：
As of version 1.6, minimizeJar will respect classes that were specifically marked for inclusion in a filter. Note that specifying an include filter for classes in an artifact implicitly excludes all non-specified classes in that artifact.
所以我只能讓shade將swt的artifact全部保留，不做優化。
<filter>
<artifact>org.eclipse:swt.win32.x86_64</artifact>
<includes>
<include>**</include>
</includes>
</filter>
或者使用artifactSet達到同樣的效果。
四、總結
- 目前shade的機制是靜態分析，所以可能會優化掉很多動態加載的類，對于使用動態加載較多的工程，在發布時需要特別注意。
- 目前shade的配置無法在一個artifact內顯式指定某個路徑不優化（或許有，但我確實沒找到，歡迎知道的朋友留言告知），只能顯式保留整個artifact不做優化。
無人分享的快樂不是真快樂，沒人分擔的痛苦是真痛苦。
posted on 2019-04-29 16:33
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