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springMVC源码分析--ModelAndViewContainer和ModelMap  

程序员文章站 2022-07-09 08:00:36
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ModelAndViewContainer主要是用来返回Model对象的,在ModelAndViewContainer中有defaultModel和redirectModel,

defaultModel是默认使用的Model,后者用于传递redirect时的参数,我们在处理中使用了Model或ModelMap时,ArgumentResolver会传入defaultModel,它是BindingAwareModelMap类型,既继承了ModelMap又实现了Model接口,所以在处理器中使用Model或者ModelMap其实使用的是同一个对象,Map参数传入的也是这个对象。处理器中RedirectAttributes类型的参数ArgumentResolver会传入redirectModel,它实际上是RedirectAttributeModelMap类型。

ModelAndViewContainer中其实就是一个ModelMap,一系列的操作都是基于ModelMap的。

public class ModelAndViewContainer {

	private boolean ignoreDefaultModelOnRedirect = false;
	
	//视图,可以是实际视图也可以是String类型的逻辑视图
	private Object view;

	//默认使用的Model
	private final ModelMap defaultModel = new BindingAwareModelMap();
	
	//redirect类型的Model
	private ModelMap redirectModel;

	private boolean redirectModelScenario = false;
	
	//用于设置SessionAttribute使用完的标志
	private final SessionStatus sessionStatus = new SimpleSessionStatus();

	//请求是否已经处理完成的标志
	private boolean requestHandled = false;


	
	public void setIgnoreDefaultModelOnRedirect(boolean ignoreDefaultModelOnRedirect) {
		this.ignoreDefaultModelOnRedirect = ignoreDefaultModelOnRedirect;
	}

	//设置视图名称
	public void setViewName(String viewName) {
		this.view = viewName;
	}

	
	public String getViewName() {
		return (this.view instanceof String ? (String) this.view : null);
	}

	
	public void setView(Object view) {
		this.view = view;
	}

	public Object getView() {
		return this.view;
	}

	public boolean isViewReference() {
		return (this.view instanceof String);
	}


	public ModelMap getModel() {
		if (useDefaultModel()) {
			return this.defaultModel;
		}
		else {
			return (this.redirectModel != null) ? this.redirectModel : new ModelMap();
		}
	}

	//和model相关的处理方法
     /*
       * 假设redirectModelScenario = R ,ignoreDefaultModelOnRedirect = I ,(redirectModel == null)= M
       * 那么(R, I, M)共有8中组合情况,useDefaultModel返回false(也就是使用redirectModel)只有三种情况:
       * (1,1,0)、(1,1,1)、(1,0,0)
       * a:如果同时设置了redirectModelScenario和ignoreDefaultModelOnRedirect为true,那么无论redirectModel
       *    是否为null,都会使用redirectModel;
       * b:如果设置了redirectModelScenario为true,而ignoreDefaultModelOnRedirect为false,同时redirectModel
       *    为null,那么也会使用redirectModel;
	*/
	private boolean useDefaultModel() {
		return (!this.redirectModelScenario || (this.redirectModel == null && !this.ignoreDefaultModelOnRedirect));
	}

	public ModelMap getDefaultModel() {
		return this.defaultModel;
	}

	public void setRedirectModel(ModelMap redirectModel) {
		this.redirectModel = redirectModel;
	}

	public void setRedirectModelScenario(boolean redirectModelScenario) {
		this.redirectModelScenario = redirectModelScenario;
	}

	public SessionStatus getSessionStatus() {
		return this.sessionStatus;
	}

	
	public void setRequestHandled(boolean requestHandled) {
		this.requestHandled = requestHandled;
	}

	
	public boolean isRequestHandled() {
		return this.requestHandled;
	}

	public ModelAndViewContainer addAttribute(String name, Object value) {
		getModel().addAttribute(name, value);
		return this;
	}


	public ModelAndViewContainer addAttribute(Object value) {
		getModel().addAttribute(value);
		return this;
	}

	public ModelAndViewContainer addAllAttributes(Map<String, ?> attributes) {
		getModel().addAllAttributes(attributes);
		return this;
	}

	public ModelAndViewContainer mergeAttributes(Map<String, ?> attributes) {
		getModel().mergeAttributes(attributes);
		return this;
	}

	public ModelAndViewContainer removeAttributes(Map<String, ?> attributes) {
		if (attributes != null) {
			for (String key : attributes.keySet()) {
				getModel().remove(key);
			}
		}
		return this;
	}

	
	public boolean containsAttribute(String name) {
		return getModel().containsAttribute(name);
	}

}
ModelMap其实就是一个HashMap而已,主要用于数据的存取而已。

@SuppressWarnings("serial")
public class ModelMap extends LinkedHashMap<String, Object> {

	
	public ModelMap() {
	}

	public ModelMap(String attributeName, Object attributeValue) {
		addAttribute(attributeName, attributeValue);
	}

	public ModelMap(Object attributeValue) {
		addAttribute(attributeValue);
	}


	public ModelMap addAttribute(String attributeName, Object attributeValue) {
		Assert.notNull(attributeName, "Model attribute name must not be null");
		put(attributeName, attributeValue);
		return this;
	}

	public ModelMap addAttribute(Object attributeValue) {
		Assert.notNull(attributeValue, "Model object must not be null");
		if (attributeValue instanceof Collection && ((Collection<?>) attributeValue).isEmpty()) {
			return this;
		}
		return addAttribute(Conventions.getVariableName(attributeValue), attributeValue);
	}

	public ModelMap addAllAttributes(Collection<?> attributeValues) {
		if (attributeValues != null) {
			for (Object attributeValue : attributeValues) {
				addAttribute(attributeValue);
			}
		}
		return this;
	}


	public ModelMap addAllAttributes(Map<String, ?> attributes) {
		if (attributes != null) {
			putAll(attributes);
		}
		return this;
	}


	public ModelMap mergeAttributes(Map<String, ?> attributes) {
		if (attributes != null) {
			for (Map.Entry<String, ?> entry : attributes.entrySet()) {
				String key = entry.getKey();
				if (!containsKey(key)) {
					put(key, entry.getValue());
				}
			}
		}
		return this;
	}

	
	public boolean containsAttribute(String attributeName) {
		return containsKey(attributeName);
	}

}