目標
- 對於幾種常見的入參方式，了解如何進行校驗以及該如何處理錯誤消息；
- 了解springboot 內置的參數異常類型，並能利用攔截器實現自定義處理；
- 能實現簡單的自定義校驗規則
一、PathVariable 校驗
在定義 Restful 風格的接口時，通常會采用 PathVariable 指定關鍵業務參數，如下：
@GetMapping("/path/{group:[a-zA-Z0-9_]+}/{userid}")
@ResponseBody
public String path(@PathVariable("group") String group, @PathVariable("userid") Integer userid) {
return group + ":" + userid;
}
{group:[a-zA-Z0-9_]+} 這樣的表達式指定了 group 必須是以大小寫字母、數字或下划線組成的字符串。
我們試着訪問一個錯誤的路徑：
GET /path/testIllegal.get/10000
此時會得到 404的響應，因此對於PathVariable 僅由正則表達式可達到校驗的目的
二、方法參數校驗
類似前面的例子，大多數情況下，我們都會直接將HTTP請求參數映射到方法參數上。
@GetMapping("/param")
@ResponseBody
public String param(@RequestParam("group")@Email String group,
@RequestParam("userid") Integer userid) {
return group + ":" + userid;
}
上面的代碼中，@RequestParam 聲明了映射，此外我們還為 group 定義了一個規則(復合Email格式)
這段代碼是否能直接使用呢？答案是否定的，為了啟用方法參數的校驗能力，還需要完成以下步驟：
- 聲明 MethodValidationPostProcessor
@Bean
public MethodValidationPostProcessor methodValidationPostProcessor() {
return new MethodValidationPostProcessor();
}
- Controller指定@Validated注解
@Controller
@RequestMapping("/validate")
@Validated
public class ValidateController {
如此之后，方法上的@Email規則才能生效。
校驗異常
如果此時我們嘗試通過非法參數進行訪問時，比如提供非Email格式的 group
會得到以下錯誤：
GET /validate/param?group=simple&userid=10000
====>
{
"timestamp": 1530955093583,
"status": 500,
"error": "Internal Server Error",
"exception": "javax.validation.ConstraintViolationException",
"message": "No message available",
"path": "/validate/param"
}
而如果參數類型錯誤，比如提供非整數的 userid，會得到：
GET /validate/param?group=simple&userid=1f
====>
{
"timestamp": 1530954430720,
"status": 400,
"error": "Bad Request",
"exception": "org.springframework.web.method.annotation.MethodArgumentTypeMismatchException",
"message": "Failed to convert value of type 'java.lang.String' to required type 'java.lang.Integer'; nested exception is java.lang.NumberFormatException: For input string: \"1f\"",
"path": "/validate/param"
}
當存在參數缺失時，由於定義的@RequestParam注解中，屬性 required=true，也將會導致失敗：
GET /validate/param?userid=10000
====>
{
"timestamp": 1530954345877,
"status": 400,
"error": "Bad Request",
"exception": "org.springframework.web.bind.MissingServletRequestParameterException",
"message": "Required String parameter 'group' is not present",
"path": "/validate/param"
}
三、表單對象校驗
頁面的表單通常比較復雜，此時可以將請求參數封裝到表單對象中，
並指定一系列對應的規則，參考JSR-303
public static class FormRequest {
@NotEmpty
@Email
private String email;
@Pattern(regexp = "[a-zA-Z0-9_]{6,30}")
private String name;
@Min(5)
@Max(199)
private int age;
上面定義的屬性中：
- email必須非空、符合Email格式規則；
- name必須為大小寫字母、數字及下划線組成，長度在6-30個；
- age必須在5-199范圍內
Controller方法中的定義：
@PostMapping("/form")
@ResponseBody
public FormRequest form(@Validated FormRequest form) {
return form;
}
@Validated指定了參數對象需要執行一系列校驗。
校驗異常
此時我們嘗試構造一些違反規則的輸入，會得到以下的結果：
{
"timestamp": 1530955713166,
"status": 400,
"error": "Bad Request",
"exception": "org.springframework.validation.BindException",
"errors": [
{
"codes": [
"Email.formRequest.email",
"Email.email",
"Email.java.lang.String",
"Email"
],
"arguments": [
{
"codes": [
"formRequest.email",
"email"
],
"arguments": null,
"defaultMessage": "email",
"code": "email"
},
[],
{
"arguments": null,
"codes": [
".*"
],
"defaultMessage": ".*"
}
],
"defaultMessage": "不是一個合法的電子郵件地址",
"objectName": "formRequest",
"field": "email",
"rejectedValue": "tecom",
"bindingFailure": false,
"code": "Email"
},
{
"codes": [
"Pattern.formRequest.name",
"Pattern.name",
"Pattern.java.lang.String",
"Pattern"
],
"arguments": [
{
"codes": [
"formRequest.name",
"name"
],
"arguments": null,
"defaultMessage": "name",
"code": "name"
},
[],
{
"arguments": null,
"codes": [
"[a-zA-Z0-9_]{6,30}"
],
"defaultMessage": "[a-zA-Z0-9_]{6,30}"
}
],
"defaultMessage": "需要匹配正則表達式\"[a-zA-Z0-9_]{6,30}\"",
"objectName": "formRequest",
"field": "name",
"rejectedValue": "fefe",
"bindingFailure": false,
"code": "Pattern"
},
{
"codes": [
"Min.formRequest.age",
"Min.age",
"Min.int",
"Min"
],
"arguments": [
{
"codes": [
"formRequest.age",
"age"
],
"arguments": null,
"defaultMessage": "age",
"code": "age"
},
5
],
"defaultMessage": "最小不能小於5",
"objectName": "formRequest",
"field": "age",
"rejectedValue": 2,
"bindingFailure": false,
"code": "Min"
}
],
"message": "Validation failed for object='formRequest'. Error count: 3",
"path": "/validate/form"
}
如果是參數類型不匹配，會得到：
{
"timestamp": 1530955359265,
"status": 400,
"error": "Bad Request",
"exception": "org.springframework.validation.BindException",
"errors": [
{
"codes": [
"typeMismatch.formRequest.age",
"typeMismatch.age",
"typeMismatch.int",
"typeMismatch"
],
"arguments": [
{
"codes": [
"formRequest.age",
"age"
],
"arguments": null,
"defaultMessage": "age",
"code": "age"
}
],
"defaultMessage": "Failed to convert property value of type 'java.lang.String'
to required type 'int' for property 'age'; nested exception is java.lang.NumberFormatException:
For input string: \"\"",
"objectName": "formRequest",
"field": "age",
"rejectedValue": "",
"bindingFailure": true,
"code": "typeMismatch"
}
],
"message": "Validation failed for object='formRequest'. Error count: 1",
"path": "/validate/form"
}
Form表單參數上，使用@Valid注解可達到同樣目的，而關於兩者的區別則是：
@Valid 基於JSR303，即 Bean Validation 1.0，由Hibernate Validator實現；
@Validated 基於JSR349，是Bean Validation 1.1，由Spring框架擴展實現；
后者做了一些增強擴展，如支持分組校驗，有興趣可參考這里。
四、RequestBody 校驗
對於直接Json消息體輸入，同樣可以定義校驗規則：
@PostMapping("/json")
@ResponseBody
public JsonRequest json(@Validated @RequestBody JsonRequest request) {
return request;
}
...
public static class JsonRequest {
@NotEmpty
@Email
private String email;
@Pattern(regexp = "[a-zA-Z0-9_]{6,30}")
private String name;
@Min(5)
@Max(199)
private int age;
校驗異常
構造一個違反規則的Json請求體進行輸入，會得到：
{
"timestamp": 1530956161314,
"status": 400,
"error": "Bad Request",
"exception": "org.springframework.web.bind.MethodArgumentNotValidException",
"errors": [
{
"codes": [
"Min.jsonRequest.age",
"Min.age",
"Min.int",
"Min"
],
"arguments": [
{
"codes": [
"jsonRequest.age",
"age"
],
"arguments": null,
"defaultMessage": "age",
"code": "age"
},
5
],
"defaultMessage": "最小不能小於5",
"objectName": "jsonRequest",
"field": "age",
"rejectedValue": 1,
"bindingFailure": false,
"code": "Min"
}
],
"message": "Validation failed for object='jsonRequest'. Error count: 1",
"path": "/validate/json"
}
此時與FormBinding的情況不同，我們得到了一個MethodArgumentNotValidException異常。
而如果發生參數類型不匹配，比如輸入age=1f，會產生以下結果：
{
"timestamp": 1530956206264,
"status": 400,
"error": "Bad Request",
"exception": "org.springframework.http.converter.HttpMessageNotReadableException",
"message": "Could not read document: Can not deserialize value of type int from String \"ff\": not a valid Integer value\n at [Source: java.io.PushbackInputStream@68dc9800; line: 2, column: 8] (through reference chain: org.zales.dmo.boot.controllers.ValidateController$JsonRequest[\"age\"]); nested exception is com.fasterxml.jackson.databind.exc.InvalidFormatException: Can not deserialize value of type int from String \"ff\": not a valid Integer value\n at [Source: java.io.PushbackInputStream@68dc9800; line: 2, column: 8] (through reference chain: org.zales.dmo.boot.controllers.ValidateController$JsonRequest[\"age\"])",
"path": "/validate/json"
}
這表明在JSON轉換過程中已經失敗！
五、自定義校驗規則
框架內預置的校驗規則可以滿足大多數場景使用，
但某些特殊情況下，你需要制作自己的校驗規則，這需要用到ContraintValidator接口。
我們以一個密碼校驗的場景作為示例，比如一個注冊表單上，
我們需要檢查 密碼輸入 與 密碼確認 是一致的。
**首先定義 PasswordEquals 注解
@Documented
@Constraint(validatedBy = { PasswordEqualsValidator.class })
@Target({ ElementType.METHOD, ElementType.FIELD, ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
public @interface PasswordEquals {
String message() default "Password is not the same";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
在表單上聲明@PasswordEquals 注解
@PasswordEquals
public class RegisterForm {
@NotEmpty
@Length(min=5,max=30)
private String username;
@NotEmpty
private String password;
@NotEmpty
private String passwordConfirm;
針對@PasswordEquals實現校驗邏輯
public class PasswordEqualsValidator implements ConstraintValidator<PasswordEquals, RegisterForm> {
@Override
public void initialize(PasswordEquals anno) {
}
@Override
public boolean isValid(RegisterForm form, ConstraintValidatorContext context) {
String passwordConfirm = form.getPasswordConfirm();
String password = form.getPassword();
boolean match = passwordConfirm != null ? passwordConfirm.equals(password) : false;
if (match) {
return true;
}
String messageTemplate = context.getDefaultConstraintMessageTemplate();
// disable default violation rule
context.disableDefaultConstraintViolation();
// assign error on password Confirm field
context.buildConstraintViolationWithTemplate(messageTemplate).addPropertyNode("passwordConfirm")
.addConstraintViolation();
return false;
}
}
如此，我們已經完成了自定義的校驗工作。
六、異常攔截器
SpringBoot 框架中可通過 @ControllerAdvice 實現Controller方法的攔截操作。
可以利用攔截能力實現一些公共的功能，比如權限檢查、頁面數據填充，以及全局的異常處理等等。
在前面的篇幅中，我們提及了各種校驗失敗所產生的異常，整理如下表：
| 異常類型 | 描述 |
|---|---|
| ConstraintViolationException | 違反約束，javax擴展定義 |
| BindException | 綁定失敗，如表單對象參數違反約束 |
| MethodArgumentNotValidException | 參數無效，如JSON請求參數違反約束 |
| MissingServletRequestParameterException | 參數缺失 |
| TypeMismatchException | 參數類型不匹配 |
如果希望對這些異常實現統一的捕獲，並返回自定義的消息，
可以參考以下的代碼片段：
@ControllerAdvice
public static class CustomExceptionHandler extends ResponseEntityExceptionHandler {
@ExceptionHandler(value = { ConstraintViolationException.class })
public ResponseEntity<String> handle(ConstraintViolationException e) {
Set<ConstraintViolation<?>> violations = e.getConstraintViolations();
StringBuilder strBuilder = new StringBuilder();
for (ConstraintViolation<?> violation : violations) {
strBuilder.append(violation.getInvalidValue() + " " + violation.getMessage() + "\n");
}
String result = strBuilder.toString();
return new ResponseEntity<String>("ConstraintViolation:" + result, HttpStatus.BAD_REQUEST);
}
@Override
protected ResponseEntity<Object> handleBindException(BindException ex, HttpHeaders headers, HttpStatus status,
WebRequest request) {
return new ResponseEntity<Object>("BindException:" + buildMessages(ex.getBindingResult()),
HttpStatus.BAD_REQUEST);
}
@Override
protected ResponseEntity<Object> handleMethodArgumentNotValid(MethodArgumentNotValidException ex,
HttpHeaders headers, HttpStatus status, WebRequest request) {
return new ResponseEntity<Object>("MethodArgumentNotValid:" + buildMessages(ex.getBindingResult()),
HttpStatus.BAD_REQUEST);
}
@Override
public ResponseEntity<Object> handleMissingServletRequestParameter(MissingServletRequestParameterException ex,
HttpHeaders headers, HttpStatus status, WebRequest request) {
return new ResponseEntity<Object>("ParamMissing:" + ex.getMessage(), HttpStatus.BAD_REQUEST);
}
@Override
protected ResponseEntity<Object> handleTypeMismatch(TypeMismatchException ex, HttpHeaders headers,
HttpStatus status, WebRequest request) {
return new ResponseEntity<Object>("TypeMissMatch:" + ex.getMessage(), HttpStatus.BAD_REQUEST);
}
private String buildMessages(BindingResult result) {
StringBuilder resultBuilder = new StringBuilder();
List<ObjectError> errors = result.getAllErrors();
if (errors != null && errors.size() > 0) {
for (ObjectError error : errors) {
if (error instanceof FieldError) {
FieldError fieldError = (FieldError) error;
String fieldName = fieldError.getField();
String fieldErrMsg = fieldError.getDefaultMessage();
resultBuilder.append(fieldName).append(" ").append(fieldErrMsg).append(";");
}
}
}
return resultBuilder.toString();
}
}
默認情況下，對於非法的參數輸入，框架會產生 **HTTP_BAD_REQUEST(status=400) ** 錯誤碼，
並輸出友好的提示消息，這對於一般情況來說已經足夠。
更多的輸入校驗及提示功能應該通過客戶端去完成(服務端僅做同步檢查)，
客戶端校驗的用戶體驗更好，而這也符合富客戶端(rich client)的發展趨勢。
參考文檔
springmvc-validation樣例
使用validation api進行操作
hibernate-validation官方文檔
Bean-Validation規范
歡迎繼續關注"美碼師的補習系列-springboot篇" ，期待更多精彩內容-