利用反射取得泛型信息
一、传统通过反射取得函数的参数和返回值
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Map;
import java.util.List;
import java.util.Set;
import sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl;
public class Foo {
public static void main(String[] args) throws Exception {
Method[] methods = Foo. class .getDeclaredMethods();
for (Method method : methods) {
Class[] paramTypeList = method.getParameterTypes();
Class returnType = method.getReturnType();
System.out.println(returnType);
for (Class clazz:paramTypeList) {
System.out.println(clazz);
}
System.out.println();
}
}
public static String test1(String str) {
return null ;
}
public static Integer test2(String str,Integer i) {
return null ;
}
}
二、在有泛型的时候，取得参数和返回值的集合类的泛型信息
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Map;
import java.util.List;
import java.util.Set;import sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl;
public class Foo {
public static void main(String[] args) throws Exception {
Method[] methods = Foo. class .getDeclaredMethods();
for (Method method : methods) {
System.out.println( " returnType: " );
Type returnType = method.getGenericReturnType();
if (returnType instanceof ParameterizedType) {
Type[] types = ((ParameterizedType)returnType).getActualTypeArguments();
for (Type type:types) {
System.out.println(type);
}
}
System.out.println( " paramTypeType: " );
Type[] paramTypeList = method.getGenericParameterTypes();
for (Type paramType : paramTypeList) {
if (paramType instanceof ParameterizedType) {
Type[] types = ((ParameterizedType)paramType).getActualTypeArguments();
for (Type type:types) {
System.out.println(type);
}
}
}
}
}
public static List < String > test3(List < Integer > list) {
return null ;
}
private static Map < String, Double > test4(Map < String, Object > map) {
return null ;
}
}
三、应用环境
例如你要写一个程序，需求把一个如下的配置文件变成一个集合类。
< config name = " Foo.DoubleBean " >
< element key = " key1 " value = " 1.1 " />
< element key = " key2 " value = " 2.2 " />
< element key = " key3 " value = " 3.3 " />
</ config >
根据用户的参数变成不同的集合类 Map<String.String> Map<String,Double> Map<String,Float>
如果你要着手开发一个框架，这样的需求会比较常见。这个时候取到setXX()函数的参数，就可以对应上边的问题了
补充：软件开发 , Java ,
