java怎么插动态图片 java动态加载插件

      但是存在一个问题是，如何将这些java资源加载到java运行环境中？
     
      后来在网上发现有两种方法，一种是通过反射机制对系统运行的ClassLoader进行操作，向其中添加运行环境。因为这个方法是protected，无法调用，所以只能通过反射机制来处理。另一种方法是通过改写ClassLoader，来加载自己的环境，然后在运行java时，通过参数-Djava.system.class.loader＝XXXX来使用自己的类加载器。

      下面是两个例子：

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/**//*
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* HelloWorld.java
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* 编译完之后，将其class文件放到C盘下 
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*/ 
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public class HelloWorld 
{
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public void print(String s) 
{
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   System.out.println("HelloWorld");
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}
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}
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/**//*
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*   PackageManager.java
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*   动态向系统类加载器中添加新环境 
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*/
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import java.io.File;
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import java.lang.reflect.Method;
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import java.net.URL;
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import java.net.URLClassLoader;
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import java.util.StringTokenizer;
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public class PackageManager 
{
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    public static final String CLASS_PATH = "classpath";
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    static URLClassLoader sysloader = (URLClassLoader)ClassLoader.getSystemClassLoader();
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    static Class sysclass = URLClassLoader.class;
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    static Method method;
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    public static void importClasspath() 
{
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      try 
{
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        StringTokenizer st = new StringTokenizer(System.getenv(CLASS_PATH), ";");
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        while(st.hasMoreTokens())
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          addURL(st.nextToken());
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      } catch(Exception ex) 
{ ex.printStackTrace(); }
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    }
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    public static void addURL(String path) 
{
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      try 
{
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        addURL((new File(path)).toURL());
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      } catch(Exception ex) 
{ ex.printStackTrace(); }
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    }
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    public static void addURL(URL u) 
{
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        try 
{
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        if(method == null) 
{
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          Class[] cs = new Class[] 
{URL.class};
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          method = sysclass.getDeclaredMethod("addURL", cs);
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          method.setAccessible(true);
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        }
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            method.invoke(sysloader,new Object[]
{ u });
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        } catch (Exception ex) 
{
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        ex.printStackTrace();
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            //throw new IOException("Error, could not add URL to system classloader");
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        }
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    }
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/** *//**
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* 动态加载环境和动态加载类方法
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*/
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public static void main(String[] args) 
{
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   // importClasspath();
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   addURL("C:\\");
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   try 
{
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    Class c = sysloader.loadClass("HelloWorld");
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    Method main = c.getDeclaredMethod("print",
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      new Class[] 
{ String.class });
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    if (main == null) 
{
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     System.out.println("main is null");
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    } else 
{
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     main.invoke(c.newInstance(), new Object[] 
{ "s" });
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    }
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   } catch (Exception e) 
{
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    e.printStackTrace();
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   }
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  }
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}
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/** *//**
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* ConfigurableClassLoader
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* 改写ClassLoader类
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* 这个好处在于，可以将所有的运行时问题，全部在程序中动态加载
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* 从而，不需要编写复杂的Java运行环境批处理文件
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*/
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import java.io.File;
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import java.lang.reflect.InvocationTargetException;
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import java.lang.reflect.Method;
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import java.net.MalformedURLException;
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import java.net.URL;
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import java.net.URLClassLoader;
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public class ConfigurableClassLoader extends URLClassLoader 
{
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   public ConfigurableClassLoader(ClassLoader parent)
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{
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     super(new URL[0], parent);
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     String property = System.getProperty("user.class.pool");
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     if (property != null) 
{
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       String[] paths = property.split(File.pathSeparator);
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       for (int i = 0; i < paths.length; ++i) 
{
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         try 
{
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           if (paths[i].startsWith("http:") || paths[i].startsWith("file:"))
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             addURL(new URL(paths[i]));
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           else
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             addURL(new File(paths[i]).toURL());
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         }
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         catch (MalformedURLException e) 
{
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           e.printStackTrace();
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         }
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       }
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     }
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   }
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   protected void addURL(URL url)
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{
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     super.addURL(url);
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   }
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   public static void main(String[] args) throws ClassNotFoundException, SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException
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{
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     Class mainClass = Class.forName(args[0], false, ClassLoader.getSystemClassLoader());
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     Method entryMethod = mainClass.getMethod("main", new Class[] 
{String[].class});
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     String[] appArgs = new String[args.length - 1];
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     System.arraycopy(args, 1, appArgs, 0, appArgs.length);
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     entryMethod.invoke(null, new Object[] 
{appArgs});
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   }
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}
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/** *//**
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* 这是对改写ClassLoader的测试方法
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*/
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import java.lang.reflect.Method;
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import java.net.URLClassLoader;
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public class TestMyClassLoader 
{
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public static void main(String[] args) 
{
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   try 
{
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    URLClassLoader sysloader = (URLClassLoader) ClassLoader
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    .getSystemClassLoader();
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    Class c = sysloader.loadClass("HelloWorld");
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    Method main = c.getDeclaredMethod("print",
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      new Class[] 
{ String.class });
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    if (main == null) 
{
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     System.out.println("main is null");
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    } else 
{
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     main.invoke(c.newInstance(), new Object[] 
{ "s" });
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    }
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   } catch (Exception e) 
{
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    e.printStackTrace();
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   }
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  }
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}
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测试时运行这个命令
java -Duser.class.pool=c:\ -Djava.system.class.loader=ConfigurableClassLoader TestMyClassLoader