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：
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@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;
}
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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
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protected void dovalidate(object bean) {
assert.state(this.validator != null, "no validator set");
set<constraintviolation<object>> result = this.validator.validate(bean);
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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
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@component
@validated
public class beanformethodvalidation {
public void validate(@notempty string name, @min(10) int age) {
system.out.println("validate, name: " + name + ", age: " + age);
}
}
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4、methodvalidationpostprocessor内部使用aop完成对方法的调用
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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());
}
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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
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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);
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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
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
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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 );
}
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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
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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 );
}
}
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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：
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putconstraints( tmpconstraints, decimalmax.class, arrays.aslist(
decimalmaxvalidatorforbigdecimal.class,
decimalmaxvalidatorforbiginteger.class,
decimalmaxvalidatorfordouble.class,
decimalmaxvalidatorforfloat.class,
decimalmaxvalidatorforlong.class,
decimalmaxvalidatorfornumber.class,
decimalmaxvalidatorforcharsequence.class,
decimalmaxvalidatorformonetaryamount.class
) );
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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服务器之家。
原文链接：https://juejin.im/post/5b408c18f265da0f894b4d47