java.beans.* 篇（1）Beans,BeanInfo,BeanDescriptor,Introspector,PropertyChangeSupport,EventHandler使用案例

 /**
     * @description: demos of jdk8 java.beans.Beans class
     * java.beans.Beans 作用：主要用来当作初始化bean 的工具，如下
     * 内部也是调用了 ClassFinder.findClass(beanName, cls);
     */
    @Test
    public void testBeans() throws IOException, ClassNotFoundException {
        User user = (User) Beans.instantiate(this.getClass().getClassLoader(), "com.foundation.one.jdk8.beans.User");
        System.out.println(user);
    }

  /**
     * @description: demos of jdk8 java.beans.Introspector class
     * java.beans.Introspector 作用：主要用获取beanInfo 的工具，
     * beanInfo 是类class的描述，是一系列XXXDescriptor()的聚合根 ，省去了自己写反射去获取描述的逻辑
     * 下面是BeanDescriptor MethodDescriptor ParameterDescriptor 例子：
     */
    @Test
    public void testIntrospectorAndBeanInfo() throws IOException, ClassNotFoundException, IntrospectionException {
        //decapitalize 将大头字母变为小写，如果连续两个大写字母，则不变，类似于spring 初始化bean name的命名规则
        String decapitalize1 = Introspector.decapitalize("HaHa");
        String decapitalize2 = Introspector.decapitalize("HAHa");
        Assert.assertEquals(decapitalize1,"haHa");
        Assert.assertEquals(decapitalize2,"HAHa");
        //获取com.foundation.one.jdk8.beans.User 类beanInfo信息
        BeanInfo beanInfo = Introspector.getBeanInfo(User.class, Introspector.USE_ALL_BEANINFO);
        //获取BeanDescriptor 相关信息
        BeanDescriptor beanDescriptor = beanInfo.getBeanDescriptor();
        System.out.println(beanDescriptor.getName());
        System.out.println(beanDescriptor.getDisplayName());
        System.out.println(beanDescriptor.getBeanClass());
        System.out.println(beanDescriptor.getCustomizerClass());
        //获取MethodDescriptor 相关信息
        MethodDescriptor[] methodDescriptors = beanInfo.getMethodDescriptors();
        for (MethodDescriptor methodDescriptor : methodDescriptors) {
            if (Objects.nonNull(methodDescriptor)) {
                System.out.println("method:" + methodDescriptor.getName());
                //获取ParameterDescriptor 相关信息 ，目前是需要各个系统实现这个方法的，默认方式如下获取会是null
                ParameterDescriptor parameterDescriptors[] = methodDescriptor.getParameterDescriptors();
                //parameterDescriptors 会是null,需要扩展实现，可使用params 获取，如下
                Parameter parameters[] = methodDescriptor.getMethod().getParameters();
                if (Objects.nonNull(parameters)) {
                    for (Parameter parameter : parameters) {
                        System.out.println("param:" + parameter.getType());
                    }
                }
            }
        }
    }

/**
 * @Author alan.wang
 * @Description: PropertyChangeSupport 测试类
 */
public class PropertyChangeSupportDemo {
    private final PropertyChangeSupport pcs = new PropertyChangeSupport(this);
    public void addPropertyChangeListener(PropertyChangeListener listener) {
        this.pcs.addPropertyChangeListener(listener);
    }
    public void removePropertyChangeListener(PropertyChangeListener listener) {
        this.pcs.removePropertyChangeListener(listener);
    }
    private String value;
    private String id ;
    public String getValue() {
        return value;
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.pcs.firePropertyChange("id",this.id,id);
        this.id = id;
    }
    public void setValue(String value) {
        this.pcs.firePropertyChange("value",this.value,value);
        this.value = value;
    }
}

/**
     * @description: demos of jdk8 java.beans.PropertyChangeSupport class
     * java.beans.PropertyChangeSupport 作用：主要用帮助类注册PropertyChangeListener 监听器
     * PropertyChangeListener 是一个接口，可以实现它作为某类的property 变动时触发的动作
     * PropertyChangeSupport ，PropertyChangeListener 例子：
     */
    @Test
    public void testPropertyChangeSupport(){
        PropertyChangeSupportDemo propertyChangeSupportDemo = new PropertyChangeSupportDemo();
        propertyChangeSupportDemo.addPropertyChangeListener((e)->{
            if(Objects.equals(e.getPropertyName(),"id")) {
                System.out.println("id old value:" + e.getOldValue());
                System.out.println("id new value:" + e.getNewValue());
            }else if(Objects.equals(e.getPropertyName(),"value")){
                System.out.println("value old value:" + e.getOldValue());
                System.out.println("value new value:" + e.getNewValue());
            }
        });
        propertyChangeSupportDemo.setId("1");
        System.out.println("-------------------break line---------------------------");
        propertyChangeSupportDemo.setId("2");
        System.out.println("-------------------break line---------------------------");
        propertyChangeSupportDemo.setValue("aaa");
        System.out.println("-------------------break line---------------------------");
        propertyChangeSupportDemo.setValue("bbb");
        System.out.println("-------------------break line---------------------------");
    }

/**
     * @description: demos of jdk8 java.beans.PropertyChangeListenerProxy class
     * java.beans.PropertyChangeListenerProxy 作用：主要是增强PropertyChangeListener，可以直接注册时绑定属性
     * 这样就可以不做属性判定
     * PropertyChangeListenerProxy 例子：
     */
    @Test
    public void testPropertyChangeListenerProxy(){
        //可以配合上面例子使用，用来注册回调函数
        PropertyChangeSupportDemo propertyChangeSupportDemo = new PropertyChangeSupportDemo();
        EventHandlerDemo eventHandlerDemo = new EventHandlerDemo();
        //直接添加id属性的listener
        propertyChangeSupportDemo.addPropertyChangeListener(new PropertyChangeListenerProxy("id",(e -> {
            System.out.println("id old value:" + e.getOldValue());
            System.out.println("id new value:" + e.getNewValue());
        })));
        //直接添加value属性的listener
        propertyChangeSupportDemo.addPropertyChangeListener(new PropertyChangeListenerProxy("value",(e -> {
            System.out.println("value old value:" + e.getOldValue());
            System.out.println("value new value:" + e.getNewValue());
        })));
        propertyChangeSupportDemo.setId("1");
        System.out.println("-------------------break line---------------------------");
        propertyChangeSupportDemo.setValue("bbb");
    }

/**
 * @Author alan.wang
 * @description: PropertyEditor 偶数类
 */
public class EvenNumber {
    public static final Class<EvenNumber>  TYPE = EvenNumber.class;
}

/**
 * @Author alan.wang
 * 进入后都会变成偶数，如果本身是偶数，则返回本身，如果不是偶数，则+1 返回
 */
public class EvenNumberPropertyEditorDemo extends PropertyEditorSupport {
    @Override
    public void setAsText(String text) throws IllegalArgumentException {
        Integer evenNumber = Integer.parseInt(text);
        if(evenNumber%2==0){
            setValue(evenNumber);
        }else {
            setValue(evenNumber+1);
        }
    }
}

/**
     * @description: demos of jdk8 java.beans.PropertyEditor class
     * java.beans.PropertyEditor 作用：主要用是对一个值进行转换，变为另一个类型或者另一个值
     * 以下是对一个数进行转换，如果是偶数则返回本身，不是偶数则+1 返回
     * PropertyEditorManager PropertyEditor 例子：
     */
    @Test
    public void testPropertyEditor(){
        PropertyEditorManager.registerEditor(EvenNumber.TYPE,EvenNumberPropertyEditorDemo.class);
        EvenNumberPropertyEditorDemo evenNumberPropertyEditorDemo = (EvenNumberPropertyEditorDemo)PropertyEditorManager.findEditor(EvenNumber.TYPE);
        evenNumberPropertyEditorDemo.addPropertyChangeListener((evt -> {
            System.out.println(evenNumberPropertyEditorDemo.getValue());
        }));
        evenNumberPropertyEditorDemo.setAsText("100");
        evenNumberPropertyEditorDemo.setAsText("101");
    }

/**
 * @Author alan.wang
 * @Desctiption: EventHandler demo 回调类
 */
public class EventHandlerDemo {
    public void print(String value) {
        System.out.println(value);
    }
}

 /**
     * @description: demos of jdk8 java.beans.EventHandler class
     * java.beans.EventHandler 作用：主要用帮助类创建一个回调类，节省了手动写注入并执行方法的代码
     * EventHandler 例子：
     */
    @Test
    public void testEventHandler(){
        //可以配合上面例子使用，用来注册回调函数
        PropertyChangeSupportDemo propertyChangeSupportDemo = new PropertyChangeSupportDemo();
        EventHandlerDemo eventHandlerDemo = new EventHandlerDemo();
        //不用EventHandler常规实现
        propertyChangeSupportDemo.addPropertyChangeListener(evt -> {
            eventHandlerDemo.print((String) evt.getNewValue());
        });
        propertyChangeSupportDemo.setValue("aaa");
        //EventHandler实现
        propertyChangeSupportDemo.addPropertyChangeListener(
                EventHandler.create(PropertyChangeListener.class,eventHandlerDemo,"print","newValue"));
        propertyChangeSupportDemo.setValue("bbb");
    }