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"> <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"> <property name="basenames"> <list> <value>errormsg</value> <value>validation_error</value> </list> </property></bean><bean id="validationExceptionResolver"/>
在项目类路径上增加：validation_error_zh_CN.properties资源文件：
#the error msg for input validation#commonfield.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
@Slf4jpublic 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")@ResponseBodypublic 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@Getterpublic 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@Getterpublic class BuyFlowerRequest { @NotEmpty(field = "花名") private String name; @Min(field = "价格", value = 1) private int price; @NotNull private List<PayType> payTypeList;} @Setter@Getterpublic 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@Getterpublic 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)@ResponseBodypublic 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);}以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持武林网。