spring自定义ArgumentResolver

参考：http://www.cnblogs.com/HD/p/4118829.html  介绍了几种传参数方式。

对于传多个对象或者List<对象>,spring mvc并没有提供默认实现。不过我们可以自定义。

参考：http://stackoverflow.com/questions/30715579/custom-spring-annotation-for-request-parameters/30716094

例子：

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
@Documented
public @interface WebParameter {

	String value() default "";
	
	boolean required() default true;
	
	String defaultValue() default ValueConstants.DEFAULT_NONE;
}

/**
 * This class is suitable for when you pass more than one object or List&lt;object>,or both of them.<br/>
 * This class does not support Array, even the property.<br/>
 * @author gche
 *
 */
public class WebParameterAnnotationArgumentResolver implements HandlerMethodArgumentResolver{
	
	private Map<Class, List<Field>> fieldMap = new WeakHashMap<Class, List<Field>>(100);
	
	@Override
	public boolean supportsParameter(MethodParameter parameter) {
		return parameter.hasParameterAnnotation(WebParameter.class);
	}

	@Override
	public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
			NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
		WebParameter anno = parameter.getParameterAnnotation(WebParameter.class);
		String name = anno.value();
		Object arg = null;
		Class parameterType = parameter.getParameterType();
		Map<String,String[]> parameterMap = webRequest.getParameterMap();
		if(parameterMap == null || parameterMap.isEmpty()){
			String defaultValue = anno.defaultValue();
			if(StringUtils.isBlank(defaultValue) && anno.required()){
				throw new Exception("no value is given for " + name + ", and it is required");
			}
			return this.convert(defaultValue, parameterType);
		}
		//student[0].name, student[1].name "student"  List<Student>
		if(List.class.isAssignableFrom(parameterType)){//List(Object)
			int size = this.getListSize(parameterMap, name);
			if(size <= 0){
				return Collections.emptyList();
			}
			arg = new ArrayList(size);
			ParameterizedType type = (ParameterizedType)parameter.getGenericParameterType();
			for(int i=0;i<size;i++){
				Object nestedArg = BeanUtils.instantiateClass((Class)type.getActualTypeArguments()[0]);
				((List)arg).add(nestedArg);
				this.setValue(nestedArg, parameterMap, name + "[" + i +"]");
			}
		}else if(parameterType.isArray()){//Object[]
			throw new Exception("array is not supported, please use List instead");
		}else{
			arg = BeanUtils.instantiateClass(parameterType);
			this.setValue(arg, parameterMap, name);
		}
		
		return arg;
	}
	
	private int getListSize(Map<String, String[]> parameterMap, String name){
		int size = -1;
		Iterator<Map.Entry<String, String[]>> it = parameterMap.entrySet().iterator();
		while(it.hasNext()){
			Map.Entry<String, String[]> entry = it.next();
			String key = entry.getKey();
			int index = key.indexOf(name + "[");
			int index2 = key.indexOf("]");
			if(index != -1){
				size = Math.max(size, Integer.valueOf(key.substring(index+(name+"[").length(), index2)));
			}
		}
		return size + 1;
	}
	
	private void setValue(Object instance, Map<String,String[]> parameterMap, String name) throws Exception{
		List<Field> fieldList = this.getFields(instance.getClass());
		for(Field field : fieldList){
			PropertyDescriptor property = BeanUtils.getPropertyDescriptor(instance.getClass(), field.getName());
			Class propertyType = property.getPropertyType();
			if(ClassUtils.isPrimitiveOrWrapper(propertyType)|| propertyType == String.class || propertyType == Date.class){
			 	String[] value = parameterMap.get(name + "." + property.getName());
			 	if(value == null || (value.length == 1 && StringUtils.isBlank(value[0]))){
			 		continue;
			 	}
				Method writeMethod = property.getWriteMethod();
				writeMethod.invoke(instance, this.convert(value[0], propertyType));
			}else if(propertyType.isArray()){
				throw new Exception("array is not supported, please use List instead");
			}else if(List.class.isAssignableFrom(propertyType)){
				//student.books
				int size = this.getListSize(parameterMap, name + "." + field.getName());
				List nestedList = size <=0 ? Collections.emptyList() : new ArrayList(size);
				Method writeMethod = property.getWriteMethod();
				writeMethod.invoke(instance, nestedList);
				for(int i=0;i<size;i++){
					Object nestedInstance = BeanUtils.instantiateClass((Class)((ParameterizedType)field.getGenericType()).getActualTypeArguments()[0]);
					nestedList.add(nestedInstance);
					this.setValue(nestedInstance, parameterMap, name + "." + field.getName() + "[" + i + "]");
				}
			}else{
				//nested object
				Object nestedInstance = BeanUtils.instantiateClass(propertyType);
				Method writeMethod = property.getWriteMethod();
				writeMethod.invoke(instance, nestedInstance);
				this.setValue(nestedInstance, parameterMap, name + "." + field.getName());
			}
		}
	}

	private Object convert(String data, Class expectedType) throws ParseException{
		data = data.trim();
		if(expectedType == byte.class || expectedType == Byte.class){
			return Byte.valueOf(data);
		}
		if(expectedType == char.class || expectedType == Character.class){
			return data.charAt(0);
		}
		if(expectedType == int.class || expectedType == Integer.class){
			return Integer.valueOf(data);
		}
		if(expectedType == float.class || expectedType == Float.class){
			return Float.valueOf(data);
		}
		if(expectedType == double.class || expectedType == Double.class){
			return Double.valueOf(data);
		}
		if(expectedType == long.class || expectedType == Long.class){
			return Long.valueOf(data);
		}
		if(expectedType == short.class || expectedType == Short.class){
			return Short.valueOf(data);
		}
		if(expectedType == boolean.class || expectedType == Boolean.class){
			return Boolean.valueOf(data);
		}
		if(expectedType == Date.class){
			//2016-05-09 10位
			//2016-05-09 22:23 16位
			char delimiter = data.trim().charAt(4);
			if(data.length() > 10){
				return DateUtils.parseDate(data, "yyyy"+delimiter+"MM"+delimiter+"dd HH:mm");
			}else{
				return DateUtils.parseDate(data, "yyyy"+delimiter+"MM"+delimiter+"dd");
			}
		}
		throw new TypeMismatchException(data, expectedType);
//		return data;
	}
	
	private List<Field> getFields(Class parameterType) {
		if(this.fieldMap.get(parameterType) != null){
			return this.fieldMap.get(parameterType);
		}
		Field[] fields = parameterType.getDeclaredFields();
		this.fieldMap.put(parameterType, Arrays.asList(fields));
		return this.fieldMap.get(parameterType);
	}
	
}

<mvc:annotation-driven>
		<mvc:argument-resolvers>
			<beans:bean class="com.xxx.WebParameterAnnotationArgumentResolver"></beans:bean>
		</mvc:argument-resolvers>
	</mvc:annotation-driven>

@RequestMapping("xxx")
public void save(@WebParameter("activity")Activity activity, @WebParameter("strategy")List<ActivityStrategy> strategy, HttpServletResponse response)

Activity和ActivityStrategy都是POJO。

在前端数据格式是这样：

{"activity.id":111,"activity.name":'test',"strategy[0].id":222,"strategy[0].name":"aaaa","strategy[1].id":333,"strategy[1].name":"bbbb"}

目前只实现了POJO和List<POJO>，支持嵌套。
由于我喜欢用List，因此没有实现数组。
PS:spring版本是4.2.4，4.1.4是不行的。