Method.invoke - Javaメソッドの動的に実行

package com.test.reflection;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * リフレクション・サンプル
 * １）指定するフィールド名のフィールド値を取得
 * ２）指定するフィールド名のフィールド値を設定
 * ３）動的にMethodを実行（Method.invoke）
 *
 */
public class TestReflection {
    public static void main(String []args) {
        
        try {
            MyClass obj = new MyClass("Hello", 20);
            
            System.out.println("****************フィールド値取得*****************");
            String userName = (String)getFieldValueByName(obj, "userName");
            int age = (Integer)getFieldValueByName(obj, "age");
            
            System.out.println(userName);
            System.out.println(age);
            
            System.out.println("****************フィールド値設定*****************");
            setFieldValueByName(obj, "userName", "新しい名だよ");
            setFieldValueByName(obj, "age", 30);
            
            System.out.println(obj.getUserName());
            System.out.println(obj.getAge());
        } catch (Exception e) {    //by Class.forName
            e.printStackTrace();
        }
    }
        
    /**
     * オブジェクトのフィールド値を取得する
     * @param object    取得する対象となるオブジェクト    
     * @param fieldName フィールド名
     * 
     */
    public static Object getFieldValueByName( 
            Object object, String fieldName) 
    throws SecurityException, NoSuchMethodException, 
    IllegalArgumentException, IllegalAccessException, InvocationTargetException {
        
        if (object == null)
            return null;
        
        Class cls = object.getClass();

        //フィールドのgetメソッド名を取得
        char firstChar = fieldName.charAt(0);
        char uFirstChar = Character.toUpperCase(firstChar);
        String getMethod = "get"
                + fieldName.replaceFirst(String.valueOf(firstChar),
                        String.valueOf(uFirstChar));
        
        //getメソッドを取得
        Method method = cls.getMethod(getMethod, null);
        //getメソッドを呼び出し、戻り値はフィールドの値になります
        Object objValue = method.invoke(object, null);
        
        return objValue;
    }
    
    /**
     * オブジェクトのフィールド値を設定する
     * @param object    対象となるオブジェクト    
     * @param fieldName フィールド名
     * 
     */
    public static void setFieldValueByName(
            Object object,
            String fieldName, 
            Object fieldValue) 
    throws SecurityException, NoSuchFieldException, IllegalArgumentException, 
    IllegalAccessException, InvocationTargetException, NoSuchMethodException {
                
        if (object == null) {
            return;
        }
        
        Class cls = object.getClass();  //オブジェクトのClass取得
        Field field = cls.getDeclaredField(fieldName);  //文字列（フィールド名）からFieldオブジェクト取得
        Class fieldType = field.getType();  //フィールドの型取得
        Class [] argTypes = {fieldType};
        Object[] argValues = {fieldValue};
        
        setFieldValueByName(cls, object, fieldName, argTypes, argValues);
    }
    
    public static void setFieldValueByName(Class cls, 
            Object object,
            String fieldName, 
            Class [] argTypes,
            Object [] argValues) 
    throws SecurityException, NoSuchFieldException, IllegalArgumentException, 
    IllegalAccessException, InvocationTargetException, NoSuchMethodException {
        if (object == null)
            return;

        //setメソッド名
        char firstChar = fieldName.charAt(0);
        char uFirstChar = Character.toUpperCase(firstChar);
        String setterMethod = "set"
                + fieldName.replaceFirst(String.valueOf(firstChar),
                        String.valueOf(uFirstChar));
        
        //setメソッド
        Method method = cls.getMethod(setterMethod, argTypes);
        //setメソッド実行（オブジェクト、パラメータ）
        method.invoke(object, argValues);
    }
}


class MyClass {
    private String userName;
    private int age;
    
    public MyClass(String userName, int age) {
        this.userName = userName;
        this.age = age;
    }
    
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
}