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Java---注解与反射

目录

前言

近期在学习 SSM 框架的过程中发现在 SSM 框架中大量用到了反射与注解的知识，要想学好 SSM 框架，必须将注解与反射熟记于心，尤其是对 Java 反射机制的理解。
对于我这种记性不好的人来说“基础不牢，地动山摇”的情况经常发生，所以就用这篇博客记录下关于注解与反射的知识，有出现错误的地方还请大家多多包涵，欢迎大家指出错误！

下面进入正题！！！

1. 什么是注解

注解可以被其他程序（比如编译器）读取

2. 内置注解

@Override: 重写

@Deprecated: 废弃

@SuppressWarnings（""）: 抑制编译时的警告信息（需要添加参数）

3. 元注解

负责注解其他注解

@Target: 被描述的注解可以用在什么地方

@Retention: 表示需要在什么级别保存改注释信息，用于描述注解的生命周期 (SOURCE<CLASS<RUNTIME) 什么时候有效

@Documented: 说明该注解将被包含在 javadoc 中

@Inherited: 说明子类可以继承父类中的该注解

4. 自定义注解

使用 @interface 自定义注解

// 自定义注解
public class Test03 {
    // 注解可以显示的赋值，如果没有默认值，我们就必须该注解赋值
    @MyAnnotation2(age = 18)
    public void test(){}
    @MyAnnotation3("ikun")
    public void Test2(){}

}


@Target({ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@interface MyAnnotation2{
// 这不是方法，是注解的参数
String name() default "";
int age() default 0;// 默认值是 -1 代表不存在
String[] schools() default {"清华","北大"};
}


@Target({ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@interface MyAnnotation3{
// 这不是方法，是注解的参数
String value();


}

5. 反射概述

  • 动态语言：就是在运行时代码可以根据某些条件改变自身结构（c#,JavaScript,php,python）

  • 静态语言: 运行时结构不可变（Java,C，C++）

在 java 中我们可以利用反射机制获得类似动态语言的特性

  • Java Reflection

6. 获得反射对象

  • 反射相关的主要 API
    java.lang.Class: 代表 - 个类
    java.lang.reftect.Method: 代表类的方法
    java.lang.reflect.Field: 代表类的成员变量
    java.lang.reflect.Constructor: 代表类的构造器
    ...

7. 得到 class 类的几种方式（重点）

Class 类
对象照镜子后可以得到的信息：某个类的属性、方法和构造器、某个类到底实现了哪些接口。
对于每个类而言，JRE 都为其保留一个不变的 Class 类型的对象。一个 Class 对象包含了特
定某个结构 (class/.interface/.enum/annotation/primitive type/.void/ 们) 的有关信息。

  • Class 本身也是一个类
  • Class 对象只能由系统建立对象
  • 一个加载的类在 JVM 中只会有一个 Class 实例
  • 一个 Class 对象对应的是一个加载到 JVM 中的一个.class 文件
  • 每个类的实例都会记得自己是由哪个 Class 实例所生成
  • 通过 Classi 可以完整地得到一个类中的所有被加载的结构
  • Class 类是 Reflection 的根源，针对任何你想动态加载、运行的类，唯有先获得相应的 Class 对象
 // 方式一：通过对象获得
        Class  c1 = person.getClass();
        System.out.println(c1.hashCode());

    <span class="hljs-comment">//方式二：forName获得（常用）</span>
    <span class="hljs-type">Class</span>  <span class="hljs-variable">c2</span> <span class="hljs-operator">=</span> Class.forName(<span class="hljs-string">"com.qjd.reflection.Student"</span>);
    System.out.println(c2.hashCode());


    <span class="hljs-comment">//方式三：通过类名.class</span>
    <span class="hljs-type">Class</span>  <span class="hljs-variable">c3</span> <span class="hljs-operator">=</span> Student.class;
    System.out.println(c3.hashCode());


    <span class="hljs-comment">//方式四：基本内置类型的包装类都有一个Type属性</span>
    <span class="hljs-type">Class</span>  <span class="hljs-variable">c4</span> <span class="hljs-operator">=</span> Integer.TYPE;
    System.out.println(c4);

8. 所有类型的 class 对象

哪些类型可以有 Class 对象

  • class: 外部类，成员（成员内部类，静态内部类），局部内部类，匿名内部类。
  • interface: 接口
  • []: 数组
  • enum: 枚举
  • annotation: 注解 @interface
  • primitive type: 基本数据类型
  • void

9. 类加载内存分析

当程序主动使用某个类时，如果该类还未被加载到内存中，则系统会通过如下三个步骤来对该类进行初始化

public class Test05 {
    public static void main(String[] args) {
        A a = new A();
        System.out.println(A.m);
        /**
         * 1. 加载到内存，会产生一个类对应 Class 对象
         * 2. 链接，链接结束后，m=0
         * 3. 初始化
         *   <clinit>{System.out.println("A 类静态代码块初始化");
         *               m=300;
         *               m=100;
         *   }
         *
         *   m=100
         *
         *
         */

}



}
class A{


    <span class="hljs-keyword">static</span>{
        System.out.println(<span class="hljs-string">"A类静态代码块初始化"</span>);
        m=<span class="hljs-number">300</span>;
    }
    <span class="hljs-comment">/*
    * m=300
    * m=100
    * */</span>
    <span class="hljs-keyword">static</span> <span class="hljs-type">int</span> <span class="hljs-variable">m</span> <span class="hljs-operator">=</span> <span class="hljs-number">100</span>;
    <span class="hljs-keyword">public</span> <span class="hljs-title function_">A</span><span class="hljs-params">()</span>{
        System.out.println(<span class="hljs-string">"A类的无参构造初始化"</span>);

    }



}

内存图分析

10. 分析类初始化

注：常量不会引发初始化

11. 类加载器

public class Test07 {
    public static void main(String[] args) throws ClassNotFoundException {
        // 获取系统类的加载器
        ClassLoader systemClassLoader = ClassLoader.getSystemClassLoader();
        System.out.println(systemClassLoader);

    <span class="hljs-comment">//获取系统类加载器的父类加载器-----》扩展类加载器</span>
    <span class="hljs-type">ClassLoader</span> <span class="hljs-variable">parent</span> <span class="hljs-operator">=</span> systemClassLoader.getParent();
    System.out.println(parent);

    <span class="hljs-comment">//获取扩展类加载器的父类加载器---》根加载器（c/c++）</span>
    <span class="hljs-type">ClassLoader</span> <span class="hljs-variable">parent1</span> <span class="hljs-operator">=</span> parent.getParent();
    System.out.println(parent1);

    <span class="hljs-comment">//测试当前类是哪个加载器加载的（系统）</span>
    <span class="hljs-type">ClassLoader</span> <span class="hljs-variable">classLoader</span> <span class="hljs-operator">=</span> Class.forName(<span class="hljs-string">"com.qjd.reflection.Test07"</span>).getClassLoader();
    System.out.println(classLoader);

    <span class="hljs-comment">//测试jdk内置的类是哪个加载器加载的（根）</span>
    classLoader = Class.forName(<span class="hljs-string">"java.lang.Object"</span>).getClassLoader();
    System.out.println(classLoader);

    <span class="hljs-comment">//如何获得系统类加载器可以加载的路径</span>
    System.out.println(System.getProperty(<span class="hljs-string">"java.class.path"</span>));
    <span class="hljs-comment">//D:\Program Files (x86)\java\jdk1.8\jre\lib\charsets.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\deploy.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\access-bridge-64.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\cldrdata.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\dnsns.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\jaccess.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\jfxrt.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\localedata.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\nashorn.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\sunec.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\sunjce_provider.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\sunmscapi.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\sunpkcs11.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\ext\zipfs.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\javaws.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\jce.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\jfr.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\jfxswt.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\jsse.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\management-agent.jar;D</span>
    <span class="hljs-comment">// :\Program Files (x86)\java\jdk1.8\jre\lib\plugin.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\resources.jar;</span>
    <span class="hljs-comment">// D:\Program Files (x86)\java\jdk1.8\jre\lib\rt.jar;</span>
    <span class="hljs-comment">// E:\SSM\反射和注解\reflect\target\classes;</span>
    <span class="hljs-comment">// E:\Java\IntelliJ IDEA 2020.3.4\lib\idea_rt.jar</span>
    
    
    <span class="hljs-comment">//双亲委派机制</span>
    <span class="hljs-comment">//（如果存在重名）检测跟加载器的包而不是自己写的</span>
}



}

12. 创建运行时类的对象（重点）

// 获得类的信息
public class Test08 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, NoSuchMethodException {
        Class c1 = Class.forName("com.qjd.reflection.User");

    <span class="hljs-comment">//获得类的名字</span>
    System.out.println(c1.getName());<span class="hljs-comment">//包名加类名</span>
    System.out.println(c1.getSimpleName());<span class="hljs-comment">//类名</span>

    <span class="hljs-comment">//获得类的属性</span>
    System.out.println(<span class="hljs-string">"==========================================================="</span>);
    Field[] fields = c1.getFields();<span class="hljs-comment">//只能找到public属性</span>

    fields = c1.getDeclaredFields();<span class="hljs-comment">//找到全部的属性</span>
    <span class="hljs-keyword">for</span> (Field field : fields) {
        System.out.println(field);
    }

    <span class="hljs-comment">//获得指定属性的值</span>
    <span class="hljs-type">Field</span> <span class="hljs-variable">name</span> <span class="hljs-operator">=</span> c1.getDeclaredField(<span class="hljs-string">"name"</span>);
    System.out.println(name);

    <span class="hljs-comment">//获得类的方法</span>
    System.out.println(<span class="hljs-string">"==========================================================="</span>);
    Method[] methods = c1.getMethods();<span class="hljs-comment">//获得本类及其父类全部的public方法</span>
    <span class="hljs-keyword">for</span> (Method method : methods) {
        System.out.println(<span class="hljs-string">"正常的"</span>+method);
    }

    Method[] declaredMethods = c1.getDeclaredMethods();<span class="hljs-comment">//获得本类的所有方法包括private方法</span>
    <span class="hljs-keyword">for</span> (Method declaredMethod : declaredMethods) {
        System.out.println(<span class="hljs-string">"declaredMethods"</span>+declaredMethod);

    }

    <span class="hljs-comment">//获得指定方法</span>
    <span class="hljs-comment">//重载</span>
    System.out.println(<span class="hljs-string">"==========================================================="</span>);
    <span class="hljs-type">Method</span> <span class="hljs-variable">getName</span> <span class="hljs-operator">=</span> c1.getMethod(<span class="hljs-string">"getName"</span>, <span class="hljs-literal">null</span>);
    <span class="hljs-type">Method</span> <span class="hljs-variable">setName</span> <span class="hljs-operator">=</span> c1.getMethod(<span class="hljs-string">"setName"</span>, String.class);
    System.out.println(getName);
    System.out.println(setName);

    <span class="hljs-comment">//获得构造器</span>
    System.out.println(<span class="hljs-string">"==========================================================="</span>);
    Constructor[] constructors = c1.getConstructors();<span class="hljs-comment">//获得public方法</span>
    <span class="hljs-keyword">for</span> (Constructor constructor : constructors) {
        System.out.println(constructor);
    }
    
    Constructor[] declaredConstructors = c1.getDeclaredConstructors();<span class="hljs-comment">//获得全部方法</span>
    <span class="hljs-keyword">for</span> (Constructor declaredConstructor : declaredConstructors) {
        System.out.println(declaredConstructor);
    }

    <span class="hljs-comment">//获得指定的构造器</span>
    <span class="hljs-type">Constructor</span> <span class="hljs-variable">declaredConstructor</span> <span class="hljs-operator">=</span> c1.getDeclaredConstructor(String.class, <span class="hljs-type">int</span>.class, <span class="hljs-type">int</span>.class);
    System.out.println(<span class="hljs-string">"指定的"</span>+declaredConstructor);

}



}

13. 动态创建对象执行方法（重点）

代码实现

// 动态创建对象，通过反射
public class Test09 {
    public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException, NoSuchFieldException {
        // 获得 Class 对象
        Class c1 = Class.forName("com.qjd.reflection.User");
        // 构造一个对象
        //User user = (User) c1.newInstance();// 本质上是调用类的无参构造器
        //System.out.println(user);

    <span class="hljs-comment">//通过构造器创建对象</span>



//        Constructor constructor = c1.getDeclaredConstructor(String.class, int.class, int.class);
//        User user2 = (User) constructor.newInstance("ikun",001,18);
//        System.out.println(user2);


    <span class="hljs-comment">//通过反射调用普通方法</span>
    <span class="hljs-type">User</span> <span class="hljs-variable">user3</span> <span class="hljs-operator">=</span> (User) c1.newInstance();
    <span class="hljs-comment">//通过反射获取一个方法</span>
    <span class="hljs-type">Method</span> <span class="hljs-variable">setName</span> <span class="hljs-operator">=</span> c1.getMethod(<span class="hljs-string">"setName"</span>, String.class);
    <span class="hljs-comment">//invoke激活</span>
    <span class="hljs-comment">//(对象，“方法的值”)</span>
    setName.invoke(user3,<span class="hljs-string">"kunkun"</span>);
    System.out.println(user3.getName());



    <span class="hljs-comment">//通过反射操作属性</span>
    System.out.println(<span class="hljs-string">"==========================================="</span>);
    <span class="hljs-type">User</span> <span class="hljs-variable">user4</span> <span class="hljs-operator">=</span> (User) c1.newInstance();
    <span class="hljs-type">Field</span> <span class="hljs-variable">name</span> <span class="hljs-operator">=</span> c1.getDeclaredField(<span class="hljs-string">"name"</span>);

    <span class="hljs-comment">//不能直接操作私有属性，我们需要关闭程序的安全检测，属性或者方法的setAccessible(true);</span>
    name.setAccessible(<span class="hljs-literal">true</span>);
    name.set(user4,<span class="hljs-string">"坤坤"</span>);
    System.out.println(user4.getName());

}



}

14. 性能对比分析

// 分析性能问题
public class Test10 {
    // 普通方式调用
    public static void test01(){
        User user = new User();

    <span class="hljs-type">long</span> <span class="hljs-variable">startTime</span> <span class="hljs-operator">=</span> System.currentTimeMillis();

    <span class="hljs-keyword">for</span> (<span class="hljs-type">int</span> <span class="hljs-variable">i</span> <span class="hljs-operator">=</span> <span class="hljs-number">0</span>; i &lt; <span class="hljs-number">1000000000</span>; i++) {
        user.getName();
    }
    <span class="hljs-type">long</span> <span class="hljs-variable">endTime</span> <span class="hljs-operator">=</span> System.currentTimeMillis();

    System.out.println(<span class="hljs-string">"普通方式执行1000000000次："</span>+(endTime-startTime)+<span class="hljs-string">"ms"</span>);
}


<span class="hljs-comment">//反射方式调用</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">test02</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> InvocationTargetException, IllegalAccessException, NoSuchMethodException {
    <span class="hljs-type">User</span> <span class="hljs-variable">user</span> <span class="hljs-operator">=</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">User</span>();
    <span class="hljs-type">Class</span> <span class="hljs-variable">c1</span> <span class="hljs-operator">=</span> user.getClass();

    <span class="hljs-type">Method</span> <span class="hljs-variable">getName</span> <span class="hljs-operator">=</span> c1.getDeclaredMethod(<span class="hljs-string">"getName"</span>, <span class="hljs-literal">null</span>);



    <span class="hljs-type">long</span> <span class="hljs-variable">startTime</span> <span class="hljs-operator">=</span> System.currentTimeMillis();

    <span class="hljs-keyword">for</span> (<span class="hljs-type">int</span> <span class="hljs-variable">i</span> <span class="hljs-operator">=</span> <span class="hljs-number">0</span>; i &lt; <span class="hljs-number">1000000000</span>; i++) {
        getName.invoke(user,<span class="hljs-literal">null</span>);
    }
    <span class="hljs-type">long</span> <span class="hljs-variable">endTime</span> <span class="hljs-operator">=</span> System.currentTimeMillis();

    System.out.println(<span class="hljs-string">"反射方式执行1000000000次："</span>+(endTime-startTime)+<span class="hljs-string">"ms"</span>);
}

<span class="hljs-comment">//反射方式调用  关闭检测</span>


<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">test03</span><span class="hljs-params">()</span> <span class="hljs-keyword">throws</span> InvocationTargetException, IllegalAccessException, NoSuchMethodException {
    <span class="hljs-type">User</span> <span class="hljs-variable">user</span> <span class="hljs-operator">=</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">User</span>();
    <span class="hljs-type">Class</span> <span class="hljs-variable">c1</span> <span class="hljs-operator">=</span> user.getClass();

    <span class="hljs-type">Method</span> <span class="hljs-variable">getName</span> <span class="hljs-operator">=</span> c1.getDeclaredMethod(<span class="hljs-string">"getName"</span>, <span class="hljs-literal">null</span>);

   getName.setAccessible(<span class="hljs-literal">true</span>);

    <span class="hljs-type">long</span> <span class="hljs-variable">startTime</span> <span class="hljs-operator">=</span> System.currentTimeMillis();

    <span class="hljs-keyword">for</span> (<span class="hljs-type">int</span> <span class="hljs-variable">i</span> <span class="hljs-operator">=</span> <span class="hljs-number">0</span>; i &lt; <span class="hljs-number">1000000000</span>; i++) {
        getName.invoke(user,<span class="hljs-literal">null</span>);
    }
    <span class="hljs-type">long</span> <span class="hljs-variable">endTime</span> <span class="hljs-operator">=</span> System.currentTimeMillis();

    System.out.println(<span class="hljs-string">"关闭检测执行1000000000次："</span>+(endTime-startTime)+<span class="hljs-string">"ms"</span>);
}

<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">main</span><span class="hljs-params">(String[] args)</span> <span class="hljs-keyword">throws</span> IllegalAccessException, NoSuchMethodException, InvocationTargetException {
    test01();
    test02();
    test03();
}



}

结果

15. 获取泛型信息

反射操作泛型

  • Java 采用泛型擦除的机制来引入泛型，Java 中的泛型仅仅是给编译器 javac 使用的，确保数据的安全性和免去强制类型转换问题，但是，一旦编译完成，所有和泛型有关的类型全部擦除

  • 为了通过反射操作这些类型，Java 新增 ParameterizedType,GenericArrayType,TypeVariable 和 WildcardType 几种类型来代表不能被归一到 Class 类中的类型但是又和原始类型齐名的类型

  • ParameterizedType: 表示一种参数化类型，比如 Collection

  • GenericArrayType: 表示一种元素类型是参数化类型或者类型变量的数组类型

  • ypeVariable: 是各种类型变量的公共父接口

  • WildcardType: 代表一种通配符类型表达式

16. 反射操作注解

ORM

// 练习反射操作注解
public class Test12 {

<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">main</span><span class="hljs-params">(String[] args)</span> <span class="hljs-keyword">throws</span> ClassNotFoundException, NoSuchFieldException {
    <span class="hljs-type">Class</span> <span class="hljs-variable">c1</span> <span class="hljs-operator">=</span> Class.forName(<span class="hljs-string">"com.qjd.reflection.Student2"</span>);

    <span class="hljs-comment">//通过反射获得注解</span>
    Annotation[] annotations = c1.getAnnotations();
    <span class="hljs-keyword">for</span> (Annotation annotation : annotations) {
        System.out.println(annotation);
    }
    <span class="hljs-comment">//获得注解的value的值</span>
   <span class="hljs-type">TableQjd</span> <span class="hljs-variable">tableQjd</span> <span class="hljs-operator">=</span> (TableQjd)c1.getAnnotation(TableQjd.class);
    <span class="hljs-type">String</span> <span class="hljs-variable">value</span> <span class="hljs-operator">=</span> tableQjd.value();
    System.out.println(value);

    <span class="hljs-comment">//获得类指定的注解</span>
    System.out.println(<span class="hljs-string">"==================="</span>);
    <span class="hljs-type">Field</span> <span class="hljs-variable">field</span> <span class="hljs-operator">=</span> c1.getDeclaredField(<span class="hljs-string">"name"</span>);
    <span class="hljs-type">FieldQjd</span> <span class="hljs-variable">annotation</span> <span class="hljs-operator">=</span> field.getAnnotation(FieldQjd.class);
    System.out.println(annotation.columnName());
    System.out.println(annotation.type());
    System.out.println(annotation.length());


}



}


@TableQjd("db_student")
class Student2{
@FieldQjd(columnName = "db_id",type = "int",length = 10)
private int id;
@FieldQjd(columnName = "db_age",type = "int",length = 10)
private int age;
@FieldQjd(columnName = "db_name",type = "varchar",length = 3)
private String name;


<span class="hljs-keyword">public</span> <span class="hljs-title function_">Student2</span><span class="hljs-params">(<span class="hljs-type">int</span> id, <span class="hljs-type">int</span> age, String name)</span> {
    <span class="hljs-built_in">this</span>.id = id;
    <span class="hljs-built_in">this</span>.age = age;
    <span class="hljs-built_in">this</span>.name = name;
}

<span class="hljs-keyword">public</span> <span class="hljs-title function_">Student2</span><span class="hljs-params">()</span> {
}

<span class="hljs-meta">@Override</span>
<span class="hljs-keyword">public</span> String <span class="hljs-title function_">toString</span><span class="hljs-params">()</span> {
    <span class="hljs-keyword">return</span> <span class="hljs-string">"Student2{"</span> +
            <span class="hljs-string">"id="</span> + id +
            <span class="hljs-string">", age="</span> + age +
            <span class="hljs-string">", name='"</span> + name + <span class="hljs-string">'\''</span> +
            <span class="hljs-string">'}'</span>;
}

<span class="hljs-keyword">public</span> <span class="hljs-type">int</span> <span class="hljs-title function_">getId</span><span class="hljs-params">()</span> {
    <span class="hljs-keyword">return</span> id;
}

<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">setId</span><span class="hljs-params">(<span class="hljs-type">int</span> id)</span> {
    <span class="hljs-built_in">this</span>.id = id;
}

<span class="hljs-keyword">public</span> <span class="hljs-type">int</span> <span class="hljs-title function_">getAge</span><span class="hljs-params">()</span> {
    <span class="hljs-keyword">return</span> age;
}

<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">setAge</span><span class="hljs-params">(<span class="hljs-type">int</span> age)</span> {
    <span class="hljs-built_in">this</span>.age = age;
}

<span class="hljs-keyword">public</span> String <span class="hljs-title function_">getName</span><span class="hljs-params">()</span> {
    <span class="hljs-keyword">return</span> name;
}

<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">setName</span><span class="hljs-params">(String name)</span> {
    <span class="hljs-built_in">this</span>.name = name;
}



}


// 类名的注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface TableQjd{
String value();
}


// 属性的注解
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface FieldQjd{
String columnName();
String type();
int length();
}

注：本文参考与 B 站 up 主遇见狂神说的讲解视频进行编写，如有遗漏和错误，欢迎大家提出
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__EOF__

  • 本文作者： 鹤鸣呦呦、、
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