struts自定义验证规则

1、Struts实现验证的过程

通过对Struts源代码的学习，总结一下Struts如何实现验证。

在struts-default.xml文件中，有validator和workflow两个拦截器。

< interceptor  name = "validation"  class = "org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor" />
< interceptor  name = "workflow"  class = "com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor" />

概括地来说，validation拦截器是做验证，而workflow拦截器是利用validator的验证规则来决定该怎么做：如果存在错误，则返回Action.INPUT，如果不返回错误，则继续执行ActionInvocation的invoke方法。

接下来，我们来仔细的探讨一下validation拦截器，它对应的类是org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor。

AnnotationValidatorInterceptor类继承自ValidationInterceptor类

public  class  AnnotationValidationInterceptor  extends  ValidationInterceptor {
    //...
}

ValidatorInterceptor类继承自MethodFilterInterceptor类

在它的类的注释中有这样的话：This interceptor runs the action through the standard validation framework, which in turn checks the action against any validation rules (found in files such as ActionClass-validation.xml) and adds field-level and action-level error messages (provided that the action implements com.opensymphony.xwork2.ValidationAware).

也就是说，如果ValidatorInterceptor类作为拦截器的时候，它会让standard validation framework check the action any validation rules，当然这些validation rules包括在ActionClass-validation中做的验证规则。

/**
*ValidationInterceptor可以引导action经过the standard validation framework。
*如果the standard validation framework查找到任何与validation rules相违背的地方，
*就会添加field-level或者是action-level的错误信息（前提是实现了ValidationAware接口）。
*This interceptor runs the action through the standard validation framework,
*which in turn checks the action against any validation rules (found in files
*such as ActionClass-validation.xml) and adds field-level and action-level error messages
*(provided that the action implements com.opensymphony.xwork2.ValidationAware).
*这个拦截器常常是拦截器栈的最后一个。
*This interceptor is often one of the last (or second to last) interceptors applied in a stack,
*as it assumes that all values have already been set on the action.
*
*如果为当前拦截器指定了excludeMethods参数，excludeMethods参数里包含的方法就不会被拦截。
*This interceptor does nothing if the name of the method being invoked is specified
*in the "excludeMethods" parameter. "excludeMethods" accepts a comma-delimited list of method names.
*For example, requests to "foo!input.action" and "foo!back.action" will be skipped by this interceptor
*if you set the "excludeMethods" parameter to "input, back".
*
*The workflow of the action request does not change due to this interceptor.
*Rather, this interceptor is often used in conjuction with the workflow interceptor.
*/
public  class  ValidationInterceptor  extends  MethodFilterInterceptor {
    //...
}

---

在上面，我们总结这样的结论：

如果ValidatorInterceptor类作为拦截器的时候，它会让standard validation framework check the action any validation rules，当然这些validation rules包括在ActionClass-validation中做的验证规则。

而AnnotationValidatorInterceptor类继承自ValidationInterceptor类，因此当java培训机构中的AnnotationValidatorInterceptor类注册为拦截器的时候，也会检验这些validation rules。

在这里要区分两个概念：验证拦截器和验证器。验证拦截器（ValidatorInterceptor），本质上就是拦截器，它的功能是：拦截住request请求，然后调用验证器(Validator)进行验证。

2、自定义验证规则 

2.1、自定义验证规则的步骤

自定义验证规则，包括3个步骤：

（1）自定义验证程序必须实现 Validator 接口

    Validator 接口有一个方法：

        void validate(java.lang.Object object)

    需要开发者进行覆盖。

    另外ValidatorSupport 、 FieldValidatorSupport 实现了 Validator 接口

    若需要普通的验证程序, 可以继承 ValidatorSupport 类

    若需要field验证程序, 可以继承 FieldValidatorSupport 类

（2）注册

    在类路径(src)下的 validators.xml 文件里注册

（3）应用

    在Action的校验文件(Action类名-validation.xml)中添加校验器

Validator接口的源代码定义如下：

public  interface  Validator {

    /**
     * The validation implementation must guarantee that setValidatorContext will
     * be called with a non-null ValidatorContext before validate is called.
     *
     * @param object the object to be validated.
     * @throws ValidationException is thrown if there is validation error(s).
     */
    void  validate(Object object)  throws  ValidationException;

    //其它代码省略。。。


}

2.2、示例

a)自定义规则类

PositiveNumberValidator.java

package  com.rk.strut.j_validation;

import  com.opensymphony.xwork2.validator.ValidationException;
import  com.opensymphony.xwork2.validator.validators.FieldValidatorSupport;

public  class  PositiveNumberValidator  extends  FieldValidatorSupport
{

    @Override
    public  void  validate(Object object)  throws  ValidationException
    {
        String fieldName = getFieldName();
        Object fieldValue =  this .getFieldValue(fieldName, object);

        if (fieldValue  instanceof  java.lang.Integer)
        {
            Integer value = Integer.parseInt(fieldValue.toString());
            //如果小于0，则添加Field Error
            if (value<= 0 )
            {
                super .addFieldError(fieldName, object);
            }
        }
    }
}

b)在src下的validators.xml下注册该规则

xml  version = "1.0"  encoding = "UTF-8" ?>

        "-//Apache Struts//XWork Validator Definition 1.0//EN"
        "http://struts.apache.org/dtds/xwork-validator-definition-1.0.dtd">

< validators >
    < validator  name = "positivenum"  class = "com.rk.strut.j_validation.PositiveNumberValidator" > validator >
validators >

c)使用校验规则

建立StudentAction.java，并在该StudentAction.java同一包下建立StudentAction-validation.xml文件中

StudentAction.java

package  com.rk.strut.j_validation;

import  com.opensymphony.xwork2.Action;
import  com.opensymphony.xwork2.ActionSupport;

public  class  StudentAction  extends  ActionSupport
{
    private  int  weight;

    public  int  getWeight()
    {
        return  weight;
    }

    public  void  setWeight( int  weight)
    {
        this .weight = weight;
    }

    @Override
    public  String execute()  throws  Exception
    {
        return  Action.SUCCESS;
    }

}

StudentAction-validation.xml

xml  version = "1.0"  encoding = "UTF-8" ?>

       "-//Apache Struts//XWork Validator 1.0//EN"
       "http://struts.apache.org/dtds/xwork-validator-1.0.dtd">
< validators >
    < field  name = "weight" >
        < field-validator  type = "positivenum" >
            < message >必须输入正数 message >
        field-validator >
    field >
validators >