Spring REST：异常处理卷。 3

这是该系列中有关Spring REST异常处理的最后一篇文章。最后，这次我将讨论在表单处理期间可能发生的REST异常的处理。因此，在本教程中，您将看到与REST，表单和异常处理有关的所有内容。客户端呢？ jQuery将用于反映REST服务的所有响应。

与以前的教程一样，我将使用Smartphone应用程序。现在是宣布此帖子主要目的的好时机– 智能手机实体需要在创建和编辑之前进行验证。

让我们看一下更新的Smartphone类：

@Entity
@Table(name="smartphones")
public class Smartphone {@Id@GeneratedValueprivate Integer id;@Length(min=1, max=20)private String producer;@Length(min=1, max=20)private String model;@Range(min=1, max=1500)private double price;/*** Method updates already existed {@link Smartphone} object with values from the inputed argument.* @param sPhone - Object which contains new Smartphone values.* @return {@link Smartphone} object to which this method applied.*/public Smartphone update(Smartphone sPhone) {this.producer = sPhone.producer;this.model = sPhone.model;this.price = sPhone.price;return this;}@Overridepublic String toString() {return producer+": "+model+" with price "+price;}//getters and setters are omitted}

请注意@Length和@Range批注。这些注释是bean验证的标准方法。在通过添加以下依赖项来更新已存在的pom.xml文件之后，可以使用这些注释：

org.hibernatehibernate-validator5.0.1.Finaljavax.validationvalidation-api1.1.0.Final

在此之后，我需要更新messages.properties文件：

Length.smartphone.producer = Length of a Smartphone producer should be from 1 to 20 characters.
Length.smartphone.model = Length of a Smartphone model should be from 1 to 20 characters.
Range.smartphone.price = Price of a Smartphone should be from 1 to 1 500.00 $

现在，让我们看一下SmartphoneController类中的createSmartphone方法：

...@RequestMapping(value="/create", method=RequestMethod.POST, produces = MediaType.APPLICATION_JSON_VALUE,consumes = MediaType.APPLICATION_JSON_VALUE)@ResponseBodypublic Smartphone createSmartphone(@RequestBody @Valid Smartphone smartphone) {return smartphoneService.create(smartphone);}
...

@Valid注释应用于方法参数。要特别注意缺少BindingResult ，它不需要像传统的Spring MVC应用程序中那样进行验证。如果Smartphone对象中的某些属性的值不合适，则@Value批注将引发MethodArgumentNotValidException 。

在实体创建/编辑期间处理异常需要使用不同的模型来表示信息。我的意思是上一篇文章中的 ErrorInfo类。我们需要传输其他信息，其中包含错误字段名称和该字段的某些错误消息。为此，这里是一个新类：

public class ErrorFormInfo {private String url;private String message;private List< FieldErrorDTO > fieldErrors = new ArrayList< FieldErrorDTO >();public ErrorFormInfo() {}public ErrorFormInfo(String url, String message) {this.url = url;this.message = message;}public ErrorFormInfo(List< FieldErrorDTO > fieldErrors, String url, String message) {this.fieldErrors = fieldErrors;this.url = url;this.message = message;}//getters and setters are omitted}

第二个类是FieldErrorDTO它在上面的代码示例中使用：

public class FieldErrorDTO {private String fieldName;private String fieldError;public FieldErrorDTO(String fieldName, String fieldError) {this.fieldName = fieldName;this.fieldError = fieldError;}//getters and setters are omitted}

引入错误传输对象后，我可以继续@ControllerAdvice类中的错误处理。这是RestExceptionProcessor类的代码片段：

...@ExceptionHandler(MethodArgumentNotValidException.class)@ResponseStatus(value=HttpStatus.BAD_REQUEST)@ResponseBodypublic ErrorFormInfo handleMethodArgumentNotValid(HttpServletRequest req, MethodArgumentNotValidException ex) {String errorMessage = localizeErrorMessage("error.bad.arguments");String errorURL = req.getRequestURL().toString();ErrorFormInfo errorInfo = new ErrorFormInfo(errorURL, errorMessage);BindingResult result = ex.getBindingResult();                List< FieldError > fieldErrors = result.getFieldErrors();errorInfo.getFieldErrors().addAll(populateFieldErrors(fieldErrors));return errorInfo;}/*** Method populates {@link List} of {@link FieldErrorDTO} objects. Each list item contains* localized error message and name of a form field which caused the exception.* Use the {@link #localizeErrorMessage(String) localizeErrorMessage} method.* * @param fieldErrorList - {@link List} of {@link FieldError} items* @return {@link List} of {@link FieldErrorDTO} items*/public List< FieldErrorDTO > populateFieldErrors(List< FieldError > fieldErrorList) {List< FieldErrorDTO > fieldErrors = new ArrayList< FieldErrorDTO >();StringBuilder errorMessage = new StringBuilder("");for (FieldError fieldError : fieldErrorList) {errorMessage.append(fieldError.getCode()).append(".");errorMessage.append(fieldError.getObjectName()).append(".");errorMessage.append(fieldError.getField());String localizedErrorMsg = localizeErrorMessage(errorMessage.toString());fieldErrors.add(new FieldErrorDTO(fieldError.getField(), localizedErrorMsg));errorMessage.delete(0, errorMessage.capacity());}return fieldErrors;}/*** Method retrieves appropriate localized error message from the {@link MessageSource}.* * @param errorCode - key of the error message* @return {@link String} localized error message */public String localizeErrorMessage(String errorCode) {Locale locale = LocaleContextHolder.getLocale();String errorMessage = messageSource.getMessage(errorCode, null, locale);return errorMessage;}
...

可以通过本文开头的链接找到RestExceptionProcessor类的完整版本。我希望上面的代码片段能自我解释。如果否，请随时在评论中提问。

我需要做的最后一件事是开发客户端代码端：

$(document).ready(function() {$('#newSmartphoneForm').submit(function(event) {var producer = $('#producer').val();var model = $('#model').val();var price = $('#price').val();var json = { "producer" : producer, "model" : model, "price": price};$.ajax({url: $("#newSmartphoneForm").attr( "action"),data: JSON.stringify(json),type: "POST",beforeSend: function(xhr) {xhr.setRequestHeader("Accept", "application/json");xhr.setRequestHeader("Content-Type", "application/json");$(".error").remove();},success: function(smartphone) {var respContent = "";respContent += "Smartphone was created: [";respContent += smartphone.producer + " : ";respContent += smartphone.model + " : " ;respContent += smartphone.price + "]";$("#sPhoneFromResponse").html(respContent);                   },error: function(jqXHR, textStatus, errorThrown) {var respBody = $.parseJSON(jqXHR.responseText);var respContent = "";respContent += "";respContent += respBody.message;respContent += "";$("#sPhoneFromResponse").html(respContent);$.each(respBody.fieldErrors, function(index, errEntity) {var tdEl = $("."+errEntity.fieldName+"-info");tdEl.html(""+errEntity.fieldError+"");});}});event.preventDefault();});});

客户端new-phone.jsp文件的完整版本可通过本文开头的链接找到。

到此为止，我必须对上面文章中开发的所有内容进行演示。因此场景很简单，我将打开“新智能手机”页面并提交包含无效数据的表单。

sr1