Simulate JDK dynamic proxy (Java design mode)

Source: Internet
Author: User

Jdk6 provides javacompiler, standardjavafilemanager,IterableCompile the. Java file.

When implementing proxy, the framework can use cglib to directly generate a binary file without generating a. Java file.

// Interface public interface moveable {void move (); void stop ();}

// Implement the moveable interface public class tank implements moveable {public void move () {system. out. println ("tank move ()... ");} public void stop () {system. out. println ("tank stop ()... ");}}

Import java. Lang. Reflect. method; // create an interface besides moveable invocationhandlerpublic interface invocationhandler {void invoke (Object o, method M );}

Import Java. lang. reflect. method; // implements the invocationhandler interface, customizes the content to be added, and creates the handlerpublic class loghandler implements invocationhandler {object target; Public loghandler (object target) implements this.tar get = target ;} public void invoke (Object o, method M) {system. out. println ("loghandler start... "); try {M. invoke (target);} catch (exception e) {e. printstacktrace ();} system. out. println ("loghandler end... ");}}

Import Java. io. file; import Java. io. filewriter; import Java. lang. reflect. constructor; import Java. lang. reflect. method; import URL; import urlclassloader; import javax. tools. javacompiler; import javax. tools. standardjavafilemanager; import javax. tools. toolprovider; // simulate JDK's proxy class proxypublic class proxy {// simulate JDK's method for creating proxy classes. There is also a classloader parameter in JDK. Here, the interface and the logic handler to be added are passed in, the result returns a proxy object. Public static object newproxyinstance (class INF, invocationhandler h) throws exception {string methodstr = ""; string RT = "\ r \ n"; method [] Methods = inf. getmethods (); For (method M: Methods) {methodstr + = "@ override" + RT + "Public void" + M. getname () + "() {" + RT + "try {" + RT + "method MD =" + INF. getname () + ". class. getmethod (\ "" + M. getname () + "\"); "+ RT +" H. invoke (this, MD); "+ RT +"} Ca Tch (exception e) {e. printstacktrace () ;}" + RT + "}" ;}// generate the proxy object class string src = "package proxy;" + RT + "Import Java. lang. reflect. method; "+ RT +" public class $ proxy1 implements "+ INF. getname () + "{" + RT + "proxy. invocationhandler h; "+ RT +" Public $ proxy1 (invocationhandler h) {"+ RT +" this. H = H; "+ RT +"} "+ RT + methodstr +"} "; string filename =" D:/share/test/Proxy/$ "; file F = new F Ile (filename); filewriter fw = new filewriter (f); FW. write (SRC); // generate. java file FW. flush (); FW. close (); // compile the class javacompiler compiler = toolprovider. getsystemjavacompiler (); standardjavafilemanager filemanager = compiler. getstandardfilemanager (null, null, null); iterable Units = filemanager. getjavafileobjects (filename); compiler. gettask (null, filemanager, null, units ). call (); // compile and generate. class file. Filemanager. close (); Url [] url = new URL [] {new URL ("file:/D:/share/test /")}; urlclassloader loader = new urlclassloader (URL); constructor c = loader. loadclass ("proxy. $ proxy1 "). getconstructor (invocationhandler. class); // The constructor has the return C. newinstance (h); // load. class file, generating objects .}}
Public class client {public static void main (string [] ARGs) throws exception {invocationhandler H = new loghandler (new tank (); // tell the proxy class what logic I need to add. Moveable M = (moveable) proxy. newproxyinstance (moveable. Class, H); // return the proxy object. M. Move (); // actually, this is the method that calls the logic-added proxy class. M. Stop ();}}

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