补习系列(4)-springboot 参数校验详解

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目标

对于几种常见的入参方式，了解如何进行校验以及该如何处理错误消息；
了解springboot 内置的参数异常类型，并能利用拦截器实现自定义处理；
能实现简单的自定义校验规则

1、PathVariable 校验

在定义 Restful 风格的接口时，一般会采用 PathVariable 指定关键业务参数，以下：java

@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。咱们试着访问一个错误的路径：git

GET /path/testIllegal.get/10000

此时会获得 404的响应，所以对于PathVariable 仅由正则表达式可达到校验的目的web

2、方法参数校验

相似前面的例子，大多数状况下，咱们都会直接将HTTP请求参数映射到方法参数上。正则表达式

@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，此外咱们还为 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？答案是否认的，为了启用方法参数的校验能力，还须要完成如下步骤：spring

声明 MethodValidationPostProcessor

@Bean
public MethodValidationPostProcessor methodValidationPostProcessor() {
     return new MethodValidationPostProcessor();
}

Controller指定**@Validated**注解

@Controller
@RequestMapping("/validate")
@Validated
public class ValidateController {

如此以后，方法上的@Email规则才能生效。json

校验异常 若是此时咱们尝试经过非法参数进行访问时，好比提供非Email格式的 group 会获得如下错误：api

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"
}

而若是参数类型错误，好比提供非整数的 userid，会获得：spring-mvc

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，因为定义的@RequestParam注解中，属性 required=true，也将会致使失败：springboot

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"
}

3、表单对象校验

页面的表单一般比较复杂，此时能够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指定了参数对象须要执行一系列校验。

校验异常 此时咱们尝试构造一些违反规则的输入，会获得如下的结果：

{
    "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": "须要匹配正则表达式\"[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"
}

若是是参数类型不匹配，会获得：

{
    "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注解可达到一样目的，而关于二者的区别则是：

@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；

后者作了一些加强扩展，如支持分组校验，有兴趣可参考这里。

4、RequestBody 校验

对于直接Json消息体输入，一样能够定义校验规则：

@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，会获得：

{
    "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的状况不一样，咱们获得了一个MethodArgumentNotValidException异常。而若是发生参数类型不匹配，好比输入age=1f，会产生如下结果：

{
    "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\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"
}

这代表在JSON转换过程当中已经失败！

5、自定义校验规则

框架内预置的校验规则能够知足大多数场景使用，但某些特殊状况下，你须要制做本身的校验规则，这须要用到ContraintValidator接口。

咱们以一个密码校验的场景做为示例，好比一个注册表单上，咱们须要检查 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
        context.disableDefaultConstraintViolation();

        // assign error on password Confirm field
        context.buildConstraintViolationWithTemplate(messageTemplate).addPropertyNode("passwordConfirm")
                .addConstraintViolation();
        return false;

    }
}

如此，咱们已经完成了自定义的校验工做。

6、异常拦截器

SpringBoot 框架中可经过 @ControllerAdvice 实现Controller方法的拦截操做。能够利用拦截能力实现一些公共的功能，好比权限检查、页面数据填充，以及全局的异常处理等等。

在前面的篇幅中，咱们说起了各类校验失败所产生的异常，整理以下表：

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

若是但愿对这些异常实现统一的捕获，并返回自定义的消息，能够参考如下的代码片断：

@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();
    }
}

默认状况下，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，这对于通常状况来讲已经足够。

更多的输入校验及提示功能应该经过客户端去完成(服务端仅作同步检查)，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。

码云同步代码

参考文档

springmvc-validation样例使用validation api进行操做 hibernate-validation官方文档 Bean-Validation规范

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