在Android開發的過程中,發現一些系統的方法無法調用,知道利用反射機制可以實現調用,今天測試成功java的反射機制,在此mark一下。
直接上代碼
package thinking.java.example_c11;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Arrays;
//: ShowMethod.java
//Using Java 1.1 reflection to show all the
//methods of a class, even if the methods are
//defined in the base class
public class ShowMethod {
static final String usage =
"usage: /n" +
"ShowMethods qualified.class.name/n" +
"To show all methods in class or: /n" +
"ShowMethods qualified.class.name word/n" +
"To search for methods involving 'word'";
public static void main(String[] args) {
System.out.println(Arrays.deepToString(args));
if(args.length < 1) {
System.out.println(usage);
System.exit(0);
}
try {
Class c = Class.forName(args[0]);
Class[] parameterTypes = new Class[1];
parameterTypes[0] = char[].class;
try {
Method tt = c.getMethod("valueOf", parameterTypes);
char[] pp = {'a','b','c','d'};
try {
String back = (String)tt.invoke(c.newInstance(), pp);
System.out.println("反射調用方法valueOf(char[])返回String: "+back);
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Method[] m = c.getMethods();
Constructor[] ctor = c.getConstructors();
if(args.length == 1) {
for (int i = 0; i < m.length; i++)
System.out.println(m[i].toString());
for (int i = 0; i < ctor.length; i++)
System.out.println(ctor[i].toString());
}
else {
for (int i = 0; i < m.length; i++)
if(m[i].toString()
.indexOf(args[1])!= -1)
System.out.println(m[i].toString());
for (int i = 0; i < ctor.length; i++)
if(ctor[i].toString()
.indexOf(args[1])!= -1)
System.out.println(ctor[i].toString());
}
} catch (ClassNotFoundException e) {
System.out.println("No such class: " + e);
}
}
}
例子的執行需要注意下:
1.如果不是在eclipse環境下,而是在命令行執行,則需要注意編譯出來的ShowMethod.class與執行路徑的關係。
需要在工程的bin目錄下執行,我的即是:/work/workspace/th-java/bin
我的class文件的位置是:/work/workspace/th-java/bin/thinking/java/example_c11
2.如果是在eclipse中執行。 則在run Configuration ->Arguments 中配置參數 java.lang.String。
部分運行結果:
[java.lang.String]
反射調用方法valueOf(char[])返回String: abcd
public boolean java.lang.String.equals(java.lang.Object)
public java.lang.String java.lang.String.toString()
public int java.lang.String.hashCode()
public int java.lang.String.compareTo(java.lang.String)
public int java.lang.String.compareTo(java.lang.Object)
public int java.lang.String.indexOf(int)
public int java.lang.String.indexOf(int,int)
public int java.lang.String.indexOf(java.lang.String)
。。。