Spring数据绑定之 WebDataBinder、ServletRequestDataBinder、WebBindingInitializer...---02

	//如果请求参数中有以_开头的,那么会取请求参数对应类型的默认值
	public static final String DEFAULT_FIELD_MARKER_PREFIX = "_";
	//如果请求参数中有以！开头的，那么会去请求参数对应值作为默认值
	public static final String DEFAULT_FIELD_DEFAULT_PREFIX = "!";
	
	@Nullable
	private String fieldMarkerPrefix = DEFAULT_FIELD_MARKER_PREFIX;
	@Nullable
	private String fieldDefaultPrefix = DEFAULT_FIELD_DEFAULT_PREFIX;

	@Override
	protected void doBind(MutablePropertyValues mpvs) {
		checkFieldDefaults(mpvs);
		checkFieldMarkers(mpvs);
		adaptEmptyArrayIndices(mpvs);
		super.doBind(mpvs);
	}

	protected void checkFieldDefaults(MutablePropertyValues mpvs) {
		String fieldDefaultPrefix = getFieldDefaultPrefix();
		if (fieldDefaultPrefix != null) {
			PropertyValue[] pvArray = mpvs.getPropertyValues();
			for (PropertyValue pv : pvArray) {

				// 若你给定的PropertyValue的属性名确实是以!打头的  那就做处理如下：
				// 如果JavaBean的该属性可写 && mpvs不存在去掉!后的同名属性，那就添加进来表示后续可以使用了（毕竟是默认值，没有精确匹配的高的）
				// 然后把带!的给移除掉（因为默认值以已经转正了~~~）
				// 其实这里就是说你可以使用！来给个默认值。比如!name表示若找不到name这个属性的时，就取它的值~~~
				// 也就是说你request里若有!name保底，也就不怕出现null值啦~
				if (pv.getName().startsWith(fieldDefaultPrefix)) {
					String field = pv.getName().substring(fieldDefaultPrefix.length());
					if (getPropertyAccessor().isWritableProperty(field) && !mpvs.contains(field)) {
						mpvs.add(field, pv.getValue());
					}
					mpvs.removePropertyValue(pv);
				}
			}
		}
	}

     // 处理_的步骤
	// 若传入的字段以_打头
	// JavaBean的这个属性可写 && mpvs木有去掉_后的属性名字
	// getEmptyValue(field, fieldType)就是根据Type类型给定默认值。
	// 比如Boolean类型默认给false，数组给空数组[]，集合给空集合，Map给空map  可以参考此类：CollectionFactory
	// 当然，这一切都是建立在你传的属性值是以_打头的基础上的，Spring才会默认帮你处理这些默认值
	protected void checkFieldMarkers(MutablePropertyValues mpvs) {
		String fieldMarkerPrefix = getFieldMarkerPrefix();
		if (fieldMarkerPrefix != null) {
			PropertyValue[] pvArray = mpvs.getPropertyValues();
			for (PropertyValue pv : pvArray) {
				if (pv.getName().startsWith(fieldMarkerPrefix)) {
					String field = pv.getName().substring(fieldMarkerPrefix.length());
					if (getPropertyAccessor().isWritableProperty(field) && !mpvs.contains(field)) {
						Class<?> fieldType = getPropertyAccessor().getPropertyType(field);
						mpvs.add(field, getEmptyValue(field, fieldType));
					}
					mpvs.removePropertyValue(pv);
				}
			}
		}
	}

	protected void bindMultipart(Map<String, List<MultipartFile>> multipartFiles, MutablePropertyValues mpvs) {
		multipartFiles.forEach((key, values) -> {
			if (values.size() == 1) {
				MultipartFile value = values.get(0);
				if (isBindEmptyMultipartFiles() || !value.isEmpty()) {
					mpvs.add(key, value);
				}
			}
			else {
				mpvs.add(key, values);
			}
		});
	}

    @Test
    public void testWebDataBinder02() throws BindException {
        People people = new People();
        WebDataBinder webDataBinder = new WebDataBinder(people);

        MutablePropertyValues mpvs = new MutablePropertyValues();
        mpvs.add("!name","大忽悠");
        mpvs.add("_age",20);

        webDataBinder.bind(mpvs);
        webDataBinder.close();

        System.out.println(people);
    }

public class ServletRequestDataBinder extends WebDataBinder {
	... // 沿用父类构造
	// 注意这个可不是父类的方法，是本类增强的~~~~意思就是kv都从request里来~~当然内部还是适配成了一个MutablePropertyValues
	public void bind(ServletRequest request) {
		// 内部最核心方法是它：WebUtils.getParametersStartingWith()  把request参数转换成一个Map
		// request.getParameterNames()
		MutablePropertyValues mpvs = new ServletRequestParameterPropertyValues(request);
		MultipartRequest multipartRequest = WebUtils.getNativeRequest(request, MultipartRequest.class);
	
		// 调用父类的bindMultipart方法，把MultipartFile都放进MutablePropertyValues里去~~~
		if (multipartRequest != null) {
			bindMultipart(multipartRequest.getMultiFileMap(), mpvs);
		}
		// 这个方法是本类流出来的一个扩展点~~~子类可以复写此方法自己往里继续添加
		// 比如ExtendedServletRequestDataBinder它就复写了这个方法，进行了增强（下面会说）  支持到了uriTemplateVariables的绑定
		addBindValues(mpvs, request);
		doBind(mpvs);
	}

	// 这个方法和父类的close方法类似，很少直接调用
	public void closeNoCatch() throws ServletRequestBindingException {
		if (getBindingResult().hasErrors()) {
			throw new ServletRequestBindingException("Errors binding onto object '" + getBindingResult().getObjectName() + "'", new BindException(getBindingResult()));
		}
	}
   
   	protected void addBindValues(MutablePropertyValues mpvs, ServletRequest request) {
	}
}

    @Test
    public void testServletRequestDataBinder03() throws BindException {
        People people = new People();
        ServletRequestDataBinder srdb = new ServletRequestDataBinder(people);
        //需要添加spring-test依赖支持
        MockHttpServletRequest mockReq = new MockHttpServletRequest();
        mockReq.addParameter("name","大忽悠");
        mockReq.addParameter("age","18");
        mockReq.addParameter("mother.name","1");
        mockReq.addParameter("mother.age","2");
        mockReq.addParameter("father.name","3");
        mockReq.addParameter("father.age","4");
        mockReq.addParameter("list","1","2","3","4");
        mockReq.addParameter("map[1]","1");
        mockReq.addParameter("map[2]","2");

        srdb.bind(mockReq);

        System.out.println(people);
    }

        mockReq.addParameter("map","{'name',1}");

// @since 3.1
public class ExtendedServletRequestDataBinder extends ServletRequestDataBinder {
	... // 沿用父类构造

	//本类的唯一方法
	@Override
	@SuppressWarnings("unchecked")
	protected void addBindValues(MutablePropertyValues mpvs, ServletRequest request) {
		// 它的值是：HandlerMapping.class.getName() + ".uriTemplateVariables";
		String attr = HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE;

		// 注意：此处是attr，而不是parameter
		Map<String, String> uriVars = (Map<String, String>) request.getAttribute(attr);
		if (uriVars != null) {
			uriVars.forEach((name, value) -> {
				
				// 若已经存在确切的key了，不会覆盖~~~~
				if (mpvs.contains(name)) {
					if (logger.isWarnEnabled()) {
						logger.warn("Skipping URI variable '" + name + "' because request contains bind value with same name.");
					}
				} else {
					mpvs.addPropertyValue(name, value);
				}
			});
		}
	}
}

    @Test
    public void testServletRequestDataBinder04() throws BindException {
        People people = new People();
        ServletRequestDataBinder srdb = new ServletRequestDataBinder(people);
        //需要添加spring-test依赖支持
        MockHttpServletRequest mockReq = new MockHttpServletRequest();
        mockReq.addParameter("name","大忽悠");
        mockReq.addParameter("age","18");
        mockReq.addParameter("birthday","2002-1-2");

        srdb.bind(mockReq);
        //检查是否在数据绑定和数据校验期间发生了异常，如果发生了则在此处抛出异常
        srdb.close();

        System.out.println(people);
    }

    @Test
    public void testServletRequestDataBinder04() throws BindException {
        People people = new People();
        ServletRequestDataBinder srdb = new ServletRequestDataBinder(people);
        //需要添加spring-test依赖支持
        MockHttpServletRequest mockReq = new MockHttpServletRequest();
        mockReq.addParameter("name","大忽悠");
        mockReq.addParameter("age","18");
        mockReq.addParameter("birthday","2002-1-2");
        
        srdb.addCustomFormatter(new DateFormatter());

        srdb.bind(mockReq);

        srdb.close();

        System.out.println(people);
    }

public class MyDatePropertyEditor extends PropertyEditorSupport {

    private static final String PATTERN = "yyyy-MM-dd";

    @Override
    public String getAsText() {
        Date date = (Date) super.getValue();
        return new SimpleDateFormat(PATTERN).format(date);
    }

    @Override
    public void setAsText(String text) throws IllegalArgumentException {
        try {
            super.setValue(new SimpleDateFormat(PATTERN).parse(text));
        } catch (ParseException e) {
            System.out.println("ParseException....................");
        }
    }
}

 srdb.registerCustomEditor(Date.class, new MyDatePropertyEditor());

public interface WebBindingInitializer {
	void initBinder(WebDataBinder binder);
	//spring 5.0之后废弃了该方法
	@Deprecated
	default void initBinder(WebDataBinder binder, WebRequest request) {
		initBinder(binder);
	}
}

public class ConfigurableWebBindingInitializer implements WebBindingInitializer {
   //默认支持级联属性
	private boolean autoGrowNestedPaths = true;
  //底层默认使用BeanWrapper 	
	private boolean directFieldAccess = false; 
  
	@Nullable
	private MessageCodesResolver messageCodesResolver;
	@Nullable
	private BindingErrorProcessor bindingErrorProcessor;
	@Nullable
	private Validator validator;
	@Nullable
	private ConversionService conversionService;
	// 此处使用的PropertyEditorRegistrar来管理的，最终都会被注册进PropertyEditorRegistry
	@Nullable
	private PropertyEditorRegistrar[] propertyEditorRegistrars;

	... //  省略所有get/set
	
	// 它做的事无非就是把配置的值都放进去而已~~
	@Override
	public void initBinder(WebDataBinder binder) {
		binder.setAutoGrowNestedPaths(this.autoGrowNestedPaths);
		if (this.directFieldAccess) {
			binder.initDirectFieldAccess();
		}
		if (this.messageCodesResolver != null) {
			binder.setMessageCodesResolver(this.messageCodesResolver);
		}
		if (this.bindingErrorProcessor != null) {
			binder.setBindingErrorProcessor(this.bindingErrorProcessor);
		}
		// 可以看到对校验器这块  内部还是做了容错的
		if (this.validator != null && binder.getTarget() != null && this.validator.supports(binder.getTarget().getClass())) {
			binder.setValidator(this.validator);
		}
		if (this.conversionService != null) {
			binder.setConversionService(this.conversionService);
		}
		if (this.propertyEditorRegistrars != null) {
			for (PropertyEditorRegistrar propertyEditorRegistrar : this.propertyEditorRegistrars) {
				propertyEditorRegistrar.registerCustomEditors(binder);
			}
		}
	}
}

// @since 3.1   注意：WebDataBinder 可是1.2就有了~
public interface WebDataBinderFactory {
	// 此处使用的是Spring自己的NativeWebRequest   后面两个参数就不解释了
	WebDataBinder createBinder(NativeWebRequest webRequest, @Nullable Object target, String objectName) throws Exception;
}

public class DefaultDataBinderFactory implements WebDataBinderFactory {
	@Nullable
	private final WebBindingInitializer initializer;
	// 注意：这是唯一构造函数
	public DefaultDataBinderFactory(@Nullable WebBindingInitializer initializer) {
		this.initializer = initializer;
	}

	// 实现接口的方法
	@Override
	@SuppressWarnings("deprecation")
	public final WebDataBinder createBinder(NativeWebRequest webRequest, @Nullable Object target, String objectName) throws Exception {

		WebDataBinder dataBinder = createBinderInstance(target, objectName, webRequest);
		
		// 可见WebDataBinder 创建好后，此处就会回调（只有一个）
		if (this.initializer != null) {
		//通过WebBindingInitializer的initBinder方法，我们可以覆盖掉dataBinder的默认配置
			this.initializer.initBinder(dataBinder, webRequest);
		}
		// 空方法 子类去实现，比如InitBinderDataBinderFactory实现了词方法
		initBinder(dataBinder, webRequest);
		return dataBinder;
	}

	//  子类可以复写，默认实现是WebRequestDataBinder
	// 比如子类ServletRequestDataBinderFactory就复写了，使用的new ExtendedServletRequestDataBinder(target, objectName)
	protected WebDataBinder createBinderInstance(@Nullable Object target, String objectName, NativeWebRequest webRequest) throws Exception 
		return new WebRequestDataBinder(target, objectName);
	}
    
    //空实现
    protected void initBinder(WebDataBinder dataBinder, NativeWebRequest webRequest)
			throws Exception {

	}
}

// @since 3.1
public class InitBinderDataBinderFactory extends DefaultDataBinderFactory {
	
	// 需要注意的是：`@InitBinder`可以标注N多个方法~  所以此处是List
	//拿到的InvocableHandlerMethod就是Controller类中标注了@InitBinder的方法
	private final List<InvocableHandlerMethod> binderMethods;

	// 此子类的唯一构造函数
	public InitBinderDataBinderFactory(@Nullable List<InvocableHandlerMethod> binderMethods, @Nullable WebBindingInitializer initializer) {
		super(initializer);
		this.binderMethods = (binderMethods != null ? binderMethods : Collections.emptyList());
	}

	// 上面知道此方法的调用方法生initializer.initBinder之后
	// 所以使用注解它生效的时机是在直接实现接口的后面的~
	@Override
	public void initBinder(WebDataBinder dataBinder, NativeWebRequest request) throws Exception {
		for (InvocableHandlerMethod binderMethod : this.binderMethods) {
			// 判断@InitBinder是否对dataBinder持有的target对象生效~~~（根据name来匹配的）
			if (isBinderMethodApplicable(binderMethod, dataBinder)) {
				// 关于目标方法执行这块---binderMethod只有一个参数为WebDataBinder,并且返回值必须为null
				Object returnValue = binderMethod.invokeForRequest(request, null, dataBinder);

				// 标注@InitBinder的方法不能有返回值
				if (returnValue != null) {
					throw new IllegalStateException("@InitBinder methods must not return a value (should be void): " + binderMethod);
				}
			}
		}
	}

	//@InitBinder有个Value值，它是个数组。它是用来匹配dataBinder.getObjectName()是否匹配的   若匹配上了，现在此注解方法就会生效
	// 若value为空，那就对所有生效~~~
	protected boolean isBinderMethodApplicable(HandlerMethod initBinderMethod, WebDataBinder dataBinder) {
		InitBinder ann = initBinderMethod.getMethodAnnotation(InitBinder.class);
		Assert.state(ann != null, "No InitBinder annotation");
		String[] names = ann.value();
		return (ObjectUtils.isEmpty(names) || ObjectUtils.containsElement(names, dataBinder.getObjectName()));
	}
}

// @since 3.1
public class ServletRequestDataBinderFactory extends InitBinderDataBinderFactory {
	public ServletRequestDataBinderFactory(@Nullable List<InvocableHandlerMethod> binderMethods, @Nullable WebBindingInitializer initializer) {
		super(binderMethods, initializer);
	}
	@Override
	protected ServletRequestDataBinder createBinderInstance(
			@Nullable Object target, String objectName, NativeWebRequest request) throws Exception  {
		return new ExtendedServletRequestDataBinder(target, objectName);
	}
}