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Spring Validation方法实现原理分析

程序员文章站 2023-12-20 20:23:52
最近要做动态数据的提交处理,即需要分析提交数据字段定义信息后才能明确对应的具体字段类型,进而做数据类型转换和字段有效性校验,然后做业务处理后提交数据库,自己开发一套校验逻辑...

最近要做动态数据的提交处理,即需要分析提交数据字段定义信息后才能明确对应的具体字段类型,进而做数据类型转换和字段有效性校验,然后做业务处理后提交数据库,自己开发一套校验逻辑的话周期太长,因此分析了spring validation的实现原理,复用了其底层花样繁多的validator,在此将分析spring validation原理的过程记录下,不深入细节

如何使用spring validation

spring bean初始化时校验bean是否符合jsr-303规范

1、手动添加beanvalidationpostprocessor bean

2、在model类中定义校验规则,如@max、@min、@notempty

3、声明bean,综合代码如下:

@bean
public beanpostprocessor beanvalidationpostprocessor() {
  return new beanvalidationpostprocessor();
}

@bean
public usermodel getusermodel() {
  usermodel usermodel = new usermodel();
  usermodel.setusername(null);
  usermodel.setpassword("123");
  return usermodel;
}

@data
class usermodel {
  @notnull(message = "username can not be null")
  @pattern(regexp = "[a-za-z0-9_]{5,10}", message = "username is illegal")
  private string username;
  @size(min = 5, max = 10, message = "password's length is illegal")
  private string password;
}

4、beanvalidationpostprocessor bean内部有个boolean类型的属性afterinitialization,默认是false,如果是false,在postprocessbeforeinitialization过程中对bean进行验证,否则在postprocessafterinitialization过程对bean进行验证

5、此种校验使用了spring的beanpostprocessor逻辑

6、校验底层调用了dovalidate方法,进一步调用validator.validate,默认validator为hibernatevalidator,validation-api包为java规范,spring默认的规范实现为hibernate-validator包,此hibernate非orm框架hibernate

protected void dovalidate(object bean) {
 assert.state(this.validator != null, "no validator set");
 set<constraintviolation<object>> result = this.validator.validate(bean);

7、hibernatevalidator默认调用validatorfactoryimpl来生成validator,后面展开将validatorfactoryimpl

支持方法级别的jsr-303规范

1、手动添加methodvalidationpostprocessor bean

2、类上加上@validated注解(也支持自定义注解,创建methodvalidationpostprocessor bean时传入)

3、在方法的参数中加上验证注解,比如@max、@min、@notempty、@notnull等,如

@component
@validated
public class beanformethodvalidation {
  public void validate(@notempty string name, @min(10) int age) {
    system.out.println("validate, name: " + name + ", age: " + age);
  }
}

4、methodvalidationpostprocessor内部使用aop完成对方法的调用

public void afterpropertiesset() {
  pointcut pointcut = new `annotationmatchingpointcut`(this.validatedannotationtype, true);
  this.advisor = new `defaultpointcutadvisor`(pointcut, createmethodvalidationadvice(this.validator));
}
protected advice createmethodvalidationadvice(@nullable validator validator) {
 return (validator != null ? new `methodvalidationinterceptor`(validator) : new methodvalidationinterceptor());
}

5、底层同样默认调用validatorfactoryimpl来生成validator,由validator完成校验

直接编码调用校验逻辑,如

public class person {
@notnull(message = "性别不能为空")
private gender gender;
@min(10)
private integer age;
...
}
validatorfactory validatorfactory = validation.builddefaultvalidatorfactory();
validator validator = validatorfactory.getvalidator();
person person = new person();
person.setgender(gender.man);
validator.validate(person);

同上,默认调用validatorfactoryimpl来生成validator,由validator完成具体校验

在spring controller方法参数中使用valid或validated注解标注待校验参数

1、先熟悉下spring的请求调用流程

Spring Validation方法实现原理分析

2、可以看到在各种resolver处理请求参数的过程中做了参数校验

3、底层统一调用了databinder的validate方法

4、databinder的作用:binder that allows for setting property values onto a target object, including support for validation and binding result analysis,也就是binder处理了request提交的字符串形式的参数,将其转换成服务端真正需要的类型,binder提供了对validation的支持,可以存放校验结果

5、databinder的validator默认在configurablewebbindinginitializer中初始化,默认使用optionalvalidatorfactorybean,该bean继承了localvalidatorfactorybean,localvalidatorfactorybean组合了validatorfactory、自定义校验属性等各种校验会用到的信息,默认使用validatorfactoryimpl来获取validator

至此,所有的线索都指向了validatorfactoryimpl,下面分析下该类

public validator `getvalidator`() {
 return `createvalidator`(
 constraintvalidatormanager.getdefaultconstraintvalidatorfactory(),
 valueextractormanager,
 validatorfactoryscopedcontext,
 methodvalidationconfiguration
 );
}
validator `createvalidator`(constraintvalidatorfactory constraintvalidatorfactory,
 valueextractormanager valueextractormanager,
 validatorfactoryscopedcontext validatorfactoryscopedcontext,
 methodvalidationconfiguration methodvalidationconfiguration) {
 
 beanmetadatamanager beanmetadatamanager = beanmetadatamanagers.computeifabsent(
 new beanmetadatamanagerkey( validatorfactoryscopedcontext.getparameternameprovider(), valueextractormanager, methodvalidationconfiguration ),
 key -> new beanmetadatamanager(
  `constrainthelper`,
  executablehelper,
  typeresolutionhelper,
  validatorfactoryscopedcontext.getparameternameprovider(),
  valueextractormanager,
  validationordergenerator,
  builddataproviders(),
  methodvalidationconfiguration
 )
 );
  
    return `new validatorimpl`(
  constraintvalidatorfactory,
  beanmetadatamanager,
  valueextractormanager,
  constraintvalidatormanager,
  validationordergenerator,
  validatorfactoryscopedcontext
 );
}
public final <t> set<constraintviolation<t>> validate(t object, class<?>... groups) {
 contracts.assertnotnull( object, messages.validatedobjectmustnotbenull() );
 sanitycheckgroups( groups );

 validationcontext<t> validationcontext = `getvalidationcontextbuilder().forvalidate( object )`;

 if ( !validationcontext.getrootbeanmetadata().hasconstraints() ) {
 return collections.emptyset();
 }

 validationorder validationorder = determinegroupvalidationorder( groups );
 valuecontext<?, object> valuecontext = `valuecontext.getlocalexecutioncontext`(
  validatorscopedcontext.getparameternameprovider(),
  object,
  validationcontext.getrootbeanmetadata(),
  pathimpl.createrootpath()
 );

 return validateincontext( validationcontext, valuecontext, validationorder );
}

1、getvalidator->createvalidator->validatorimpl->validate

在执行过程中封装了beanmetadatamanager、validationcontext、valuecontext等内容,都是校验时会用到的上下文信息,如待校验bean的所有校验项(含父类和接口)、property、method parameter的校验信息,从validatorfactoryscopedcontext继承过来的validator通用的各种工具类(如message、script等的处理)等,内容比较复杂

2、分组(group)校验忽略,来到默认分组处理validateconstraintsfordefaultgroup->validateconstraintsforsingledefaultgroupelement->validatemetaconstraint(注:metaconstraints维护了该bean类型及其父类、接口的所有校验,需要遍历调用validatemetaconstraint)

3、继续调用metaconstraint的dovalidateconstraint方法,根据不同的annotation type走不同的constrainttree

public static <u extends annotation> constrainttree<u> of(constraintdescriptorimpl<u> composingdescriptor, type validatedvaluetype) {
 if ( composingdescriptor.getcomposingconstraintimpls().isempty() ) {
 return new simpleconstrainttree<>( composingdescriptor, validatedvaluetype );
 }
 else {
 return new composingconstrainttree<>( composingdescriptor, validatedvaluetype );
 }
}

4、具体哪些走simple,哪些走composing暂且不管,因为二者都调用了constrainttree的'getinitializedconstraintvalidator'方法,该步用来获取校验annotation(如decimalmax、notempty等)对应的validator并初始化validator

5、 constrainthelper 类维护了所有builtin的validator,并根据校验annotation(如decimalmax)分类,validator的描述类中维护了该validator的泛型模板(如bigdecimal),如下:

putconstraints( tmpconstraints, decimalmax.class, arrays.aslist(
 decimalmaxvalidatorforbigdecimal.class,
 decimalmaxvalidatorforbiginteger.class,
 decimalmaxvalidatorfordouble.class,
 decimalmaxvalidatorforfloat.class,
 decimalmaxvalidatorforlong.class,
 decimalmaxvalidatorfornumber.class,
 decimalmaxvalidatorforcharsequence.class,
 decimalmaxvalidatorformonetaryamount.class
) );

在获取具体bean类的validator时,先根据annotation获取所有的validator,对应方法是constraintmanager.findmatchingvalidatordescriptor,然后根据被校验对象的类型获取唯一的validator

6、然后根据上下文信息initializevalidator,进而调用validator的isvalid方法校验

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。

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