2021年02月20日反射

 

☆20201110反射(tomcat)   //tomcat如何反射

 

java核心卷反射练习

 

 

 

代码:练习 java核心卷答应

package mianshi_0219;


import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Scanner;

/**
 * 这个项目用反射打印一个类的所有信息
 * @author Administrator
 *
 */
public class ReflectionTest {
    public static void main(String[] args) {
        //read class name from command line args or user input 从命令行参数和人们输入的,打印类名
        String name;
        if(args.length > 0){
            name = args[0];
        }else {
            Scanner in = new Scanner(System.in);
            System.out.println("Enter class name(e.g. java.util.Date):");
            name = in.next();
        }

        try {
            Class cl = Class.forName(name);

            Class supercl = cl.getSuperclass();
            String modeifiers = Modifier.toString(cl.getModifiers());
            if(modeifiers.length() > 0 ){
                System.out.print(modeifiers + " ");
            }
            System.out.print("class " + name);
            if (supercl != null && supercl != Object.class) {
                System.out.print(" extends " + supercl.getName());
            }

            System.out.print("\n{\n");
            printConstructors(cl);
            System.out.println();
            printMethods(cl);
            System.out.println();
            printFields(cl);
            System.out.println("}");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        System.exit(0);
    }
/**
 * prints all constructor of a class 打印类的所有构造器
 * @param cl
 */
    public static void printConstructors(Class cl) {
        Constructor[] constructors = cl.getDeclaredConstructors();
        for (Constructor c : constructors) {
            String name = c.getName();
            System.out.print(" ");
            String modifiers = Modifier.toString(c.getModifiers());
            if (modifiers.length() > 0) {
                System.out.print(modifiers + " ");
            }
            System.out.print(name + "(");

            Class[] paramTypes = c.getParameterTypes();
            for (int j = 0; j < paramTypes.length; j++) {
                if (j > 0) {
                    System.out.print(", ");
                }
                System.out.print(paramTypes[j].getName());
            }
            System.out.println(");");
        }
    }

/**
 * 打印类的所有方法
 * @param cl
 */
    public static void printMethods(Class cl)
    {
        Method[] methods = cl.getDeclaredMethods() ;
        for (Method m : methods)
        {
            Class retType = m.getReturnType();
            String name = m. getName();
            System.out.print(" ");

            String modifiers = Modifier.toString(m.getModifiers());
            if (modifiers.length() > 0) {
                System.out.print(modifiers + " ");
            }
                    System. out.print(retType. getName() + " " + name + "(");

            Class[] paramTypes = m.getParameterTypes();
            for (int j = 0; j < paramTypes.length; j++)
            {
                if (j > 0) {
                    System.out.print(" , ");
                }
                System.out.print(paramTypes[j].getName());
            }
            System.out.println(") ;");
        }
    }

/**
 * prints all fields of a class
 * @param cl
 */
    public static void printFields(Class cl) {
        Field[] fields = cl.getDeclaredFields();
        for (Field f : fields) {
            Class type = f.getType();
            String name = f.getName();
            System.out.print(" ");
            String modifiers = Modifier.toString(f.getModifiers());
            if (modifiers.length() > 0) {
                System.out.print(modifiers + " ");
            }
            System.out.println(type.getName() + " " + name + ";");
        }
    }
}