最近在项目中有这样一个需求，为了分析某些文件的产权信息，需要对项目中所有的文件生成相对应的.ip文件，当在eclipse中package explorer中selectedChange的时候，调用该project/folder/file下所有文件，生成相应的.ip文件。但是问题出现了，每次package explorer中selectedChange的时候，都需要生成一次.ip文件，而大多数情况，这个都是没有必要的(对于已经Build过的文件，如果该文件上一次Build后没有改变,Build是没有意义的),对于较大的项目，这在效率上是难以接受的，为了对于已经Build，并且在Build后没有改变的文件，我们完全可以不再Build，在这里，我们可以借用ant的解决方案：Ant通过比较类文件和源文件的时间戳来最小化编译工作。类似的，我们可以通过比较Build生成的文件和原文件的时间戳来实现：如果原文件修改时间在Build生成文件修改时间之前，则不需要Build，否则需要Build(不存在的文件时间戳设为-1)。 抽象出来，这个解决方案还是挺有用的，在很多场合可以通过这种方法判断是否需要生成新的文件，避免重复生成文件，提高了效率。
下面是程序片段：
package com.ibm.crl.ariadne.ipmanagement.util;
import java.io.File; import org.eclipse.core.resources.IFile; import org.eclipse.core.resources.IWorkspaceRoot; import org.eclipse.core.resources.ResourcesPlugin; import org.eclipse.core.runtime.IPath; import org.eclipse.core.runtime.Path;
public class BuildUtil { /** * @author suqiang * @param artifact * @return the value whether the artifact need to be Built */ public static boolean needBeBuilt(IFile artifact){ //if the file is not the java/htm/gif/jpg/jar file, it need not built. String artifactName = artifact.getName(); if(!(artifactName.endsWith(".java")|artifactName.endsWith(".jar"))) return false;
IPath relativeProjectPath = artifact.getProjectRelativePath(); IPath projectFullPath = artifact.getProject().getFullPath(); IWorkspaceRoot root = ResourcesPlugin.getWorkspace().getRoot(); IFile ipFile = (IFile)root.getFile(new Path(projectFullPath.toString()+"/.ip/"+relativeProjectPath.toString()+".ip"));
//transform from IFile to File in order to get the lastModified time,the method getLocalTimeStamp of IResource is unreliable //More in eclipse document:Note that due to varying file system timing granularities, //this value is not guaranteed to change every time the file is modified. File artifactFile = artifact.getLocation().toFile(); File ipFileFile = ipFile.getLocation().toFile();
long buildFileTimeStamp = ipFileFile.lastModified(); long sourceTimeStamp = artifactFile.lastModified(); //if the artifact has been built before and the artifact itself is not modified,it needn't be build again if(buildFileTimeStamp>=sourceTimeStamp) return false; else return true; } }
优化前： The build process cost 31828ms (core) The build process cost 31109ms (core) The build process cost 114640ms (ui) The build process cost 113406ms (ui) 优化后： The ip file is exist: The build process cost 94ms (core) The build process cost 78ms (core) The build process cost 374ms (ui) The build process cost 359ms (ui) delete the ip file: The build process cost 32219ms (core) The build process cost 37828ms (core) The build process cost 133906ms (ui) The build process cost 134438ms (ui)
以下是一些测试的结果数据(取了两个非常庞大的项目core and ui)