Additions to Java Reflection: bridging methods and some tool classes in spring

In a previous Article blog post: http://www.cnblogs.com/guangshan/p/4660564.html

There are some places in the source code.

This.bridgedmethod = Bridgemethodresolver.findbridgedmethod (method);

So what is Bridgedmethod?

After finding out, this is called bridging method: http://freish.iteye.com/blog/1158008

The Java compiler uses the bridge approach to compatibility with non-generic usages where generics are supposed to be used.

The following code:

 Public classTestbridgemethod { Public Static voidMain (string[] args) {p P=NewS (); P.test (NewObject ()); }}classP<t> {     Publict Test (T t) {returnT; }}classSextendsP<string>{@Override Publicstring Test (String t) {returnT; }}

P refers to an object of S, but the return value of S's test method is a string, there is no generic in jdk1.4, and the P.test (new object) is not checked so that it is reported at the time of the call ClassCastException

When declaring p, using p<string> p will not have such a problem.

To be compatible with non-generic code, the Java compiler generates two methods for test. Look at the following code:

ImportJava.lang.reflect.Method;Importjava.util.Arrays; Public classTestbridgemethod { Public Static voidMain (string[] args) {Class<?> clazz = S.class; Method[] Methods=Clazz.getmethods ();  for(Method method:methods) {System.out.println (Method.getname ()+ ":" + arrays.tostring (Method.getparametertypes ()) +Method.isbridge ()); }    }}classP<t> {     Publict Test (T t) {returnT; }}classSextendsP<string>{@Override Publicstring Test (String t) {returnT; }}

The result of the operation is:

Test:[class Java.lang.string]false

Test:[class Java.lang.object]true

Getclass:[]false

Hashcode:[]false

Equals:[class Java.lang.object]false

Tostring:[]false

Notify:[]false

Notifyall:[]false

Wait:[long, Int]false

Wait:[]false

Wait:[long]false

The compiler generates two test methods for S, one parameter is string, and is used for generics. One parameter is object, which is used for non-generics, and this method is the bridge method, which calls Method.isbridge to return true.

The previously mentioned failure to use generics correctly results in cross-type checking, which is caused by bridging methods.

There are also some useful collections of util tools in the spring source code:

Http://www.cnblogs.com/younggun/p/3247262.html

Additions to Java Reflection: bridging methods and some tool classes in spring