检测类路径下是否存在jar包中的class冲突，通常用于web应用的lib目录下class冲突检查

ClassConflictCheck.java

package liq.utils;

import java.io.File;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
/**
 * 检测classPath下的类冲突，通常用于web应用的lib目录下jar包中class冲突检测，
 * 避免程序运行过程中出现如下的类似异常:
 *  {@link NoSuchMethodError}、{@link NoSuchMethodException}
 *  {@link ClassNotFoundException}、{@link NoClassDefFoundError}
 *  
 * @author 0532
 *
 */
public class ClassConflictCheck {
    private static Map<String, HashSet<String>> classMap = new HashMap<String, HashSet<String>>();

    public static void check(String classPath) throws Exception {
        File dir = new File(classPath);
        File[] jarFiles = dir.listFiles();
        for (File jarFile : jarFiles) {
            if (jarFile.getName().endsWith(".jar")) {
                JarFile jar = new JarFile(jarFile);
                Enumeration<JarEntry> enumeration = jar.entries();
                while (enumeration.hasMoreElements()) {
                    JarEntry jarEntry = enumeration.nextElement();
                    if (jarEntry.getName().endsWith(".class")) {
                        storeClassAndJarRel(jarEntry.getName(), jar.getName());
                    }
                }
            }
        }
    }

    private static void storeClassAndJarRel(String className, String jarName) {
        HashSet<String> jarSet = classMap.get(className);
        if (jarSet == null) {
            jarSet = new HashSet<String>();
        }
        jarSet.add(jarName.substring(jarName.lastIndexOf("/") + 1));
        classMap.put(className, jarSet);
    }

    
    public static void main(String[] args) throws Exception {
        //args = new String[] { "/Users/soft/tomcat-7.0.54.1/deploy/cloud-mobile-cloudapi-gateway/WEB-INF/lib" };
        for (String arg : args) {
            check(arg);
        }

        boolean isConflict = false;
        for (Iterator<Map.Entry<String, HashSet<String>>> iterator = classMap.entrySet().iterator(); iterator
                .hasNext();) {
            Map.Entry<String, HashSet<String>> entry = iterator.next();
            HashSet<String> jarSet = entry.getValue();
            if (jarSet.size() > 1) {
                if (!isConflict) {
                    isConflict = true;
                }
                List<String> jarList = Arrays.asList(jarSet.toArray(new String[] {}));
                System.out.println("Class conflict!!! the class :" + entry.getKey()
                        + " has been duplicate inclusioned in the jars : " + jarList);
            }
        }

        if(!isConflict) {
            System.out.println("oh,good! there are no class conflict in the jars");
        }
    }

}

用于检测多个Jar包冲突的class

当一个项目使用的jar包较多时，代码经常在运行的时候抛出异常：java.lang.NoSuchMethodException，java.lang.ClassNotFoundException，基本是存在多个jar包包含相同的class类文件导致的，运行期引用的class由于版本没对上导致没有该方法等

该小工具可以帮助你检测出classpath下，通常是项目的lib目录下是否存在类冲突，且告诉你冲突的jar包，方便定位处理。

使用说明，示例：

cd liq/util

javac ClassConflictCheck.java

java ClassConflictCheck xxx/WEB-INF/lib

如果没有任何类冲突，则输出: "oh,good! there are no class conflict in the jars"

否则则有类似如下的冲突输出 （两处冲突了）：

Class conflict!!! the class :org/aspectj/weaver/tools/MatchingContext.class has been duplicate inclusioned in the jars : [aspectjweaver-1.6.6.jar, eclipse.aspectj__aspectjweaver-1.5.2a.jar-0.0.0.jar, aspectjtools-1.6.2.jar, aspectjweaver-1.6.2.jar]

Class conflict!!! the class :org/apache/batik/css/engine/value/css2/FontSizeAdjustManager.class has been duplicate inclusioned in the jars : [xml.xmlgraphics-1.7.jar, xml.xmlgraphics__batik-css-1.7.jar-1.7.jar]