一、PathVariable 校验
在定义 Restful 风格的接口时，通常会采用 PathVariable 指定关键业务参数，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_]+} 这样的表达式指定了 group 必须是以大小写字母、数字或下划线组成的字符串。
我们试着访问一个错误的路径：
GET /path/testIllegal.get/10000此时会得到 404的响应，因此对于PathVariable 仅由正则表达式可达到校验的目的
二、方法参数校验
类似前面的例子，大多数情况下，我们都会直接将HTTP请求参数映射到方法参数上。
@GetMapping("/param")
@ResponseBody
public String param(@RequestParam("group")@Email String group,
@RequestParam("userid") Integer userid) {
return group + ":" + userid;
}上面的代码中，@RequestParam 声明了映射，此外我们还为 group 定义了一个规则(复合Email格式)
这段代码是否能直接使用呢？答案是否定的，为了启用方法参数的校验能力，还需要完成以下步骤：
- 声明 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规则才能生效。
校验异常
如果此时我们尝试通过非法参数进行访问时，比如提供非Email格式的 group
会得到以下错误：
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"
}而如果参数类型错误，比如提供非整数的 userid，会得到：
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"
}当存在参数缺失时，由于定义的@RequestParam注解中，属性 required=true，也将会导致失败：
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、表单对象校验
页面的表单通常比较复杂，此时可以将请求参数封装到表单对象中，
并指定一系列对应的规则，参考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;上面定义的属性中：
- email必须非空、符合Email格式规则；
- name必须为大小写字母、数字及下划线组成，长度在6-30个；
- age必须在5-199范围内
Controller方法中的定义：
@PostMapping("/form")
@ResponseBody
public FormRequest form(@Validated FormRequest form) {
return form;
}@Validated指定了参数对象需要执行一系列校验。
校验异常
此时我们尝试构造一些违反规则的输入，会得到以下的结果：
{
"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": "不是一个合法的电子邮件地址",
"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": "需要匹配正则表达式"[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": "最小不能小于5",
"objectName": "formRequest",
"field": "age",
"rejectedValue": 2,
"bindingFailure": false,
"code": "Min"
}
],
"message": "Validation failed for object='formRequest'. Error count: 3",
"path": "/validate/form"
}
如果是参数类型不匹配，会得到：
{
"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表单参数上，使用@Valid注解可达到同样目的，而关于两者的区别则是：
@Valid 基于JSR303，即 Bean Validation 1.0，由Hibernate Validator实现；
@Validated 基于JSR349，是Bean Validation 1.1，由Spring框架扩展实现；
后者做了一些增强扩展，如支持分组校验，有兴趣可参考这里。
四、RequestBody 校验
对于直接Json消息体输入，同样可以定义校验规则：
@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;校验异常
构造一个违反规则的Json请求体进行输入，会得到：
{
"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": "最小不能小于5",
"objectName": "jsonRequest",
"field": "age",
"rejectedValue": 1,
"bindingFailure": false,
"code": "Min"
}
],
"message": "Validation failed for object='jsonRequest'. Error count: 1",
"path": "/validate/json"
}
此时与FormBinding的情况不同，我们得到了一个MethodArgumentNotValidException异常。
而如果发生参数类型不匹配，比如输入age=1f，会产生以下结果：
{
"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
at [Source: java.io.PushbackInputStream@68dc9800; line: 2, column: 8] (through reference chain: org.zales.dmo.boot.controllers.ValidateController$JsonRequest["age"]); nested exception is com.fasterxml.jackson.databind.exc.InvalidFormatException: Can not deserialize value of type int from String "ff": not a valid Integer value
at [Source: java.io.PushbackInputStream@68dc9800; line: 2, column: 8] (through reference chain: org.zales.dmo.boot.controllers.ValidateController$JsonRequest["age"])",
"path": "/validate/json"
}这表明在JSON转换过程中已经失败！
五、自定义校验规则
框架内预置的校验规则可以满足大多数场景使用，
但某些特殊情况下，你需要制作自己的校验规则，这需要用到ContraintValidator接口。
我们以一个密码校验的场景作为示例，比如一个注册表单上，
我们需要检查 密码输入 与 密码确认 是一致的。
**首先定义 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 {};
}在表单上声明@PasswordEquals 注解
@PasswordEquals
public class RegisterForm {
@NotEmpty
@Length(min=5,max=30)
private String username;
@NotEmpty
private String password;
@NotEmpty
private String passwordConfirm;针对@PasswordEquals实现校验逻辑
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 [ 禁用默认违规规则]
context.disableDefaultConstraintViolation();
// assign error on password Confirm field
context.buildConstraintViolationWithTemplate(messageTemplate).addPropertyNode("passwordConfirm")
.addConstraintViolation();
return false;
}
}
如此，我们已经完成了自定义的校验工作。
六、异常拦截器
SpringBoot 框架中可通过 @ControllerAdvice 实现Controller方法的拦截操作。
可以利用拦截能力实现一些公共的功能，比如权限检查、页面数据填充，以及全局的异常处理等等。
在前面的篇幅中，我们提及了各种校验失败所产生的异常，整理如下表：
| 异常类型 | 描述 |
|---|---|
| ConstraintViolationException | 违反约束，javax扩展定义 |
| BindException | 绑定失败，如表单对象参数违反约束 |
| MethodArgumentNotValidException | 参数无效，如JSON请求参数违反约束 |
| MissingServletRequestParameterException | 参数缺失 |
| TypeMismatchException | 参数类型不匹配 |
如果希望对这些异常实现统一的捕获，并返回自定义的消息，
可以参考以下的代码片段：
@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() + "
");
}
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();
}
}默认情况下，对于非法的参数输入，框架会产生 HTTP_BAD_REQUEST(status=400) 错误码，
并输出友好的提示消息，这对于一般情况来说已经足够。
更多的输入校验及提示功能应该通过客户端去完成(服务端仅做同步检查)，
客户端校验的用户体验更好，而这也符合富客户端(rich client)的发展趋势。
参考文档
springmvc-validation样例
使用validation api进行操作
hibernate-validation官方文档
Bean-Validation规范