动态加载类库

package cp;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.net.MalformedURLException;import java.net.URL;import java.net.URLClassLoader;public class AddJar2ClassPath {        //此方法虽然改变了classpath，但是不能load Jar用于当前classloader    private void updateClassPath(){        Classpath   classPath   =   new Classpath(System.getProperty("java.class.path"));            System.out.println(System.getProperty("java.class.path"));        classPath.addClasspath(System.getProperty("user.dir")+"/lib/activemq-all-5.10.0.jar");        System.setProperty("java.class.path",   classPath.toString());                   System.out.println(System.getProperty("java.class.path"));        ClassLoader   classloader   =   classPath.getClassLoader();          Thread.currentThread().setContextClassLoader(classloader);       }        //此方法load Jar后可以用于当前classloader    private void loadJar(){        URL urls;        try {            urls = new URL("file:/"+System.getProperty("user.dir")+"/lib/activemq-all-5.10.0.jar");            //GetPI.class              URLClassLoader urlLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();              Class<URLClassLoader> sysclass = URLClassLoader.class;               Method method = sysclass.getDeclaredMethod("addURL", new Class[]{URL.class});              method.setAccessible(true);              method.invoke(urlLoader, urls);                         urls = new URL("file:/"+System.getProperty("user.dir")+"/lib/images.jar");            method.invoke(urlLoader, urls);                         urls = new URL("file:/"+System.getProperty("user.dir")+"/lib/poi-3.11-20141221.jar");            method.invoke(urlLoader, urls);         } catch (MalformedURLException e) {            e.printStackTrace();        } catch (SecurityException e) {            e.printStackTrace();        } catch (NoSuchMethodException e) {            e.printStackTrace();        } catch (IllegalArgumentException e) {            e.printStackTrace();        } catch (IllegalAccessException e) {            e.printStackTrace();        } catch (InvocationTargetException e) {            e.printStackTrace();        }      }}

package cp;import   java.io.File;  import   java.io.IOException;  import   java.net.MalformedURLException;  import   java.net.URL;  import   java.net.URLClassLoader;  import   java.util.StringTokenizer;  import   java.util.Vector;   /**    *   Class   to   handle   CLASSPATH   construction    */  public   class   Classpath   {          Vector   _elements   =   new   Vector();          public   Classpath()   {}          public   Classpath(String   initial)   {                  addClasspath(initial);          }          public   boolean   addComponent(String   component)   {                  if   ((component   !=   null)   &&   (component.length()   >   0))   {                          try   {                                  File   f   =   new   File(component);                                  if   (f.exists())   {                                          File   key   =   f.getCanonicalFile();                                          if   (!_elements.contains(key))   {                                                  _elements.add(key);                                                  return   true;                                          }                                  }                          }   catch   (IOException   e)   {}                  }                  return   false;          }          public   boolean   addComponent(File   component)   {                  if   (component   !=   null)   {                          try   {                                  if   (component.exists())   {                                          File   key   =   component.getCanonicalFile();                                          if   (!_elements.contains(key))   {                                                  _elements.add(key);                                                  return   true;                                          }                                  }                          }   catch   (IOException   e)   {}                  }                  return   false;          }          public   boolean   addClasspath(String   s)   {                  boolean   added   =   false;                  if   (s   !=   null)   {                          StringTokenizer   t   =   new   StringTokenizer(s,   File.pathSeparator);                          while   (t.hasMoreTokens())   {                                  added   |=   addComponent(t.nextToken());                          }                  }                  return   added;          }          public   String   toString()   {                  StringBuffer   cp   =   new   StringBuffer(1024);                  int   cnt   =   _elements.size();                  if   (cnt   >=   1)   {                          cp.append(((File)   (_elements.elementAt(0))).getPath());                  }                  for   (int   i   =   1;   i   <   cnt;   i++)   {                          cp.append(File.pathSeparatorChar);                          cp.append(((File)   (_elements.elementAt(i))).getPath());                  }                  return   cp.toString();          }          public   URL[]   getUrls()   {                  int   cnt   =   _elements.size();                  URL[]   urls   =   new   URL[cnt];                  for   (int   i   =   0;   i   <   cnt;   i++)   {                          try   {                                  urls[i]   =   ((File)   (_elements.elementAt(i))).toURL();                          }   catch   (MalformedURLException   e)   {}                  }                  return   urls;          }          public   ClassLoader   getClassLoader()   {                  URL[]   urls   =   getUrls();                  ClassLoader   parent   =   Thread.currentThread().getContextClassLoader();                  if   (parent   ==   null)   {                          parent   =   Classpath.class.getClassLoader();                  }                  if   (parent   ==   null)   {                          parent   =   ClassLoader.getSystemClassLoader();                  }                  return   new   URLClassLoader(urls,   parent);          }  }   

private void loadJar(){        try {                URLClassLoader urlLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();              Class<URLClassLoader> sysclass = URLClassLoader.class;               Method method = sysclass.getDeclaredMethod("addURL", new Class[]{URL.class});              method.setAccessible(true);                          //TODO 如果Jar不在classpath里面才添加            //System.out.println(System.getProperty("java.class.path"));            String classpath=System.getProperty("java.class.path");                        String libDir=System.getProperty("user.dir")+"/lib";            File libDirFile=new File(libDir);            if(libDirFile.isDirectory()){                File[] libs=libDirFile.listFiles(new FileFilter() {                    public boolean accept(File file) {                        if (file.getName().endsWith(".jar")) {                            return true;                        }                        return false;                    }                });                URL urls;                if(libs!=null&&classpath!=null)                    for(int i=0;i<libs.length;i++){                        if(!classpath.contains(libs[i].getName())){                            System.out.println("Libarary is not found in classpath:"+libs[i].getName());                            urls = new URL("file:/"+libDir+"/"+libs[i].getName());                            method.invoke(urlLoader, urls);                         }                    }                else                    System.out.println("检查并加载类包："+libDir+"目录为null或者classpath为null！");            }            //            URL urls = new URL("file:/"+System.getProperty("user.dir")+"/lib/activemq-all-5.10.0.jar");//            method.invoke(urlLoader, urls); //            //            urls = new URL("file:/"+System.getProperty("user.dir")+"/lib/images.jar");//            method.invoke(urlLoader, urls); //            //            urls = new URL("file:/"+System.getProperty("user.dir")+"/lib/poi-3.11-20141221.jar");//            method.invoke(urlLoader, urls);         } catch (MalformedURLException e) {            e.printStackTrace();        } catch (SecurityException e) {            e.printStackTrace();        } catch (NoSuchMethodException e) {            e.printStackTrace();        } catch (IllegalArgumentException e) {            e.printStackTrace();        } catch (IllegalAccessException e) {            e.printStackTrace();        } catch (InvocationTargetException e) {            e.printStackTrace();        }      }