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);
}
