springMVC引入Validation的具体步骤详解

本文简单介绍如何引入validation的步骤，如何通过自定义validation减少代码量，提高生产力。特别提及：非基本类型属性的valid，GET方法的处理，validation错误信息的统一resolve。

本文中validation的实际实现委托给Hibernate validation处理

基本配置

pom引入maven依赖

<!-- validation begin -->
<dependency>
 <groupId>javax.validation</groupId>
 <artifactId>validation-api</artifactId>
 <version>1.1.0.Final</version>
</dependency>
<dependency>
 <groupId>org.hibernate</groupId>
 <artifactId>hibernate-validator</artifactId>
 <version>5.4.0.Final</version>
</dependency>
<!-- validation end -->

增加validation配置

在spring-mvc-servlet.xml中增加如下配置:

<mvc:annotation-driven validator="validator">

<bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean">
 <property name="providerClass" value="org.hibernate.validator.HibernateValidator" />
 <property name="validationMessageSource" ref="messageSource"/>
</bean>
//messageSource 为i18n资源管理bean，见applicationContext.xml配置

自定义exceptionHandler

个性化处理validation错误信息,返回给调用方的信息更加友好， 在applicationContext.xml中增加如下配置:

<!-- 加载i18n消息资源文件 -->
<bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
 <property name="basenames">
   <list>
     <value>errormsg</value>
     <value>validation_error</value>
   </list>
 </property>
</bean>

<bean id="validationExceptionResolver" class="com.*.exception.ValidationExceptionResovler"/>

在项目类路径上增加：validation_error_zh_CN.properties资源文件：

#the error msg for input validation
#common
field.can.not.be.null={field}不能为空
field.can.not.be.empty={field}不能为空或者空字符串
field.must.be.greater.than.min={field}不能小于{value}
field.must.be.letter.than.max={field}不能大于{value}

ValidationExceptionResovler实现：

ValidationExceptionResovler.java

@Slf4j
public class ValidationExceptionResovler extends AbstractHandlerExceptionResolver {
 public ValidationExceptionResovler() {
   // 设置order，在DefaultHandlerExceptionResolver之前执行
   this.setOrder(0);
 }
 /**
  * Handle the case where an argument annotated with {@code @Valid} such as
  * an {@link } or {@link } argument fails validation.
  * <p>
  * 自定义ValidationException 异常处理器
  * 获取到具体的validation 错误信息，并组装CommonResponse，返回给调用方。
  *
  * @param request current HTTP request
  * @param response current HTTP response
  * @param handler the executed handler
  * @return an empty ModelAndView indicating the exception was handled
  * @throws IOException potentially thrown from response.sendError()
  */
 @ResponseBody
 protected ModelAndView handleMethodArgumentNotValidException(BindingResult bindingResult,
                                HttpServletRequest request,
                                HttpServletResponse response,
                                Object handler)
     throws IOException {

List<ObjectError> errors = bindingResult.getAllErrors();
   StringBuffer errmsgBF = new StringBuffer();
   for (ObjectError error : errors) {
     String massage = error.getDefaultMessage();
     errmsgBF.append(massage);
     errmsgBF.append("||");
   }
   String errmsgString = errmsgBF.toString();
   errmsgString = errmsgString.length() > 2 ? errmsgString.substring(0, errmsgString.length() - 2) : errmsgString;
   log.error("Validation failed! {} ", errmsgString);

Map<String, Object> map = new TreeMap<String, Object>();
   map.put("success", false);
   map.put("errorCode", "9999");
   map.put("errorMsg", errmsgString);

ModelAndView mav = new ModelAndView();
   MappingJackson2JsonView view = new MappingJackson2JsonView();
   view.setAttributesMap(map);
   mav.setView(view);

return mav;
 }

@Override
 protected ModelAndView doResolveException(HttpServletRequest request,
                      HttpServletResponse response, Object handler,
                      Exception ex) {
   BindingResult bindingResult = null;
   if (ex instanceof MethodArgumentNotValidException) {
     bindingResult = ((MethodArgumentNotValidException) ex).getBindingResult();
   } else if(ex instanceof BindException) {
     bindingResult = ((BindException) ex).getBindingResult();
   } else {
     //other exception , ignore
   }

if(bindingResult != null) {
     try {
       return handleMethodArgumentNotValidException(bindingResult, request, response, handler);
     } catch (IOException e) {
       log.error("doResolveException: ", e);
     }
   }
   return null;
 }
}

在controller中增加@Valid 

@RequestMapping("/buy")
@ResponseBody
public BaseResponse buy(@RequestBody @Valid BuyFlowerRequest request) throws Exception {
//......
}

在request bean上为需要validation的属性增加validation注解

@Setter
@Getter
public class BuyFlowerRequest {

@NotEmpty(message = "{name.can.not.be.null}")
private String name;
}

二级对象的validation

上面的写法，只能对BuyFlowerRequest在基本类型属性上做校验,但是没有办法对对象属性的属性进行validation,如果需要对二级对象的属性进行validation,则需要在二级对象及二级对象属性上同时添加@Valid 和 具体的validation注解.

如下写法:

@Setter
@Getter
public class BuyFlowerRequest {
 @NotEmpty(field = "花名")
 private String name;

@Min(field = "价格", value = 1)
 private int price;

@NotNull
 private List<PayType> payTypeList;

}

@Setter
@Getter
public class PayType {

@Valid
 @Min(value = 1)
 private int payType;

@Valid
 @Min(value = 1)
 private int payAmount;
}

进一步减少编码量

为了减少编码工作量,通过自定义Validation注解,尝试将validation作用的filed名称传递到 错误信息的资源文件中,从而避免为每个域编写不同的message模版.

下面以重写的@NotNull为例讲解:

1、定义Validation注解,注意相比原生注解增加了field(),用于传递被validated的filed名字

NotNull.java

@Target( { ElementType.METHOD, ElementType.FIELD, ElementType.ANNOTATION_TYPE, ElementType.CONSTRUCTOR, ElementType.PARAMETER })
@Constraint(validatedBy = { NotNullValidator.class })
@Retention(RetentionPolicy.RUNTIME)
public @interface NotNull {
 String field() default "";
 String message() default "{field.can.not.be.null}";
 Class<?>[] groups() default {};
 Class<? extends Payload>[] payload() default {};
}

2、定义Validator,所有的Validator均实现ConstraintValidator接口:

NotNullValidator.java

public class NotNullValidator implements ConstraintValidator<NotNull, Object> {

@Override
 public void initialize(NotNull annotation) {

}

@Override
 public boolean isValid(Object str, ConstraintValidatorContext constraintValidatorContext) {
   return str != null;
 }
}

3、在filed上加入Validation注解,注意指定filed值,message如果没有个性化需求，可以不用指明，validation组件会自行填充default message。

BuyFlowerRequest.java

@Setter
@Getter
public class BuyFlowerRequest {

@NotEmpty(field = "花名")
 private String name;

@Min(field = "价格", value = 1)
 private int price;
}

注：@NotNull注解已经支持对list的特殊校验，对于List类型节点，如果list==null || list.size() == 0都会返回false，validation失败。目前已按照此思路自定义实现了@NotNull、@NotEmpty、@Min、@Max注解,在goods工程中可以找到.

支持GET请求

上面的示例都是POST请求，@RequestBody可以 resolve POST请求，但是不支持GET请求，阅读spring的文档和源码，发现@ModelAttribute可以将GET请求resolve成Bean，且支持Validation。具体可以翻阅spring源码：ModelAttributeMethodProcessor.resolveArgument()方法。

使用示例：

@RequestMapping(value = "/buy", method = RequestMethod.GET)
@ResponseBody
public BaseResponse detail(@Valid @ModelAttribute DetailFlowerRequest request) throws Exception {

DetailFlowerResponse response = new DetailFlowerResponse();
 response.setName(request.getName());

return ResultFactory.success(response, BaseResponse.class);
}

TODO

1、根据业务场景扩展validation,如:日期格式、金额等

2、支持多个field关系校验的validation

 附：spring validation实现关键代码

@RequestBody

实现类：RequestResponseBodyMethodProcessor.java

public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
Object arg = this.readWithMessageConverters(webRequest, parameter, parameter.getGenericParameterType());
String name = Conventions.getVariableNameForParameter(parameter);
WebDataBinder binder = binderFactory.createBinder(webRequest, arg, name);
if (arg != null) {
this.validateIfApplicable(binder, parameter);
if (binder.getBindingResult().hasErrors() && this.isBindExceptionRequired(binder, parameter)) {
 throw new MethodArgumentNotValidException(parameter, binder.getBindingResult());
}
}
mavContainer.addAttribute(BindingResult.MODEL_KEY_PREFIX + name, binder.getBindingResult());
return arg;
}

@ModelAttibute

实现类：ModelAttributeMethodProcessor.java

public final Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
String name = ModelFactory.getNameForParameter(parameter);
Object attribute = mavContainer.containsAttribute(name) ? mavContainer.getModel().get(name) : this.createAttribute(name, parameter, binderFactory, webRequest);
if (!mavContainer.isBindingDisabled(name)) {
ModelAttribute ann = (ModelAttribute)parameter.getParameterAnnotation(ModelAttribute.class);
if (ann != null && !ann.binding()) {
 mavContainer.setBindingDisabled(name);
}
}
WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name);
if (binder.getTarget() != null) {
if (!mavContainer.isBindingDisabled(name)) {
 this.bindRequestParameters(binder, webRequest);
}
this.validateIfApplicable(binder, parameter);
if (binder.getBindingResult().hasErrors() && this.isBindExceptionRequired(binder, parameter)) {
 throw new BindException(binder.getBindingResult());
}
}
Map<String, Object> bindingResultModel = binder.getBindingResult().getModel();
mavContainer.removeAttributes(bindingResultModel);
mavContainer.addAllAttributes(bindingResultModel);
return binder.convertIfNecessary(binder.getTarget(), parameter.getParameterType(), parameter);
}

来源：http://www.cnblogs.com/daoqidelv/p/9061862.html