7.验证器

输入验证是Spring处理的最重要的Web开发任务之一

验证器属于Object级，它决定某一个对象中的所有field是否均是有效的，以及是否遵循某些规则

1.Spring的验证器

要实现org.springframework.validation.Validator接口

public interface Validator{
     boolean supports(Class<?> clazz);
     void validate(Object target,Errors errors);   
}

如果验证器可以处理指定的Class，supports方法将返回true，

validate方法会验证目标对象，并将验证错误填入Errors对象

给Errors对象添加错误的最容易方法是

调用reject，往FieldError中添加一个ObjectError和rejectError

只给reject或者rejectValue传入一个错误码，Spring就会在属性文件中查找错误码，

获得相应的信息

2.ValidateUtils类

org.springframework.validation.ValidationUtils类是一个工具类

有助于编写Spring验证器，

不需要

if(firstName==null || firstName.isEmpty()){
     errors.rejectValue("price");   
}

可以用
ValidateUtils.rejectIfEmpty("price");

3.Spring的Validate范例

package app07a.domain;
import java.io.Serializable;
import java.util.Date;

public class Product implements Serializable {
    private static final long serialVersionUID = 748392348L;
    private String name;
    private String description;
    private Float price;
    private Date productionDate;

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getDescription() {
        return description;
    }
    public void setDescription(String description) {
        this.description = description;
    }
    public Float getPrice() {
        return price;
    }
    public void setPrice(Float price) {
        this.price = price;
    }
    public Date getProductionDate() {
        return productionDate;
    }
    public void setProductionDate(Date productionDate) {
        this.productionDate = productionDate;
    }
    
}

package app07a.validator;

import java.util.Date;

import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;

import app07a.domain.Product;

public class ProductValidator implements Validator {

    @Override
    public boolean supports(Class<?> klass) {
        return Product.class.isAssignableFrom(klass);
    }

    @Override
    public void validate(Object target, Errors errors) {
        Product product = (Product) target;
        ValidationUtils.rejectIfEmpty(errors, "name", "productname.required");
        ValidationUtils.rejectIfEmpty(errors, "price", "price.required");
        ValidationUtils.rejectIfEmpty(errors, "productionDate", "productiondate.required");
        
        Float price = product.getPrice();
        if (price != null && price < 0) {
            errors.rejectValue("price", "price.negative");
        }
        Date productionDate = product.getProductionDate();
        if (productionDate != null) {
            // The hour,minute,second components of productionDate are 0
            if (productionDate.after(new Date())) {
                System.out.println("salah lagi");
                errors.rejectValue("productionDate", "productiondate.invalid");
            }
        }
    }
}

验证器不需要显示注册，但是如果想要某个属性文件中获取错误消息，

则需要通过声明messageSource bean，告诉Spring去哪找这个文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd     
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">

    <context:component-scan base-package="app07a.controller" />
    <context:component-scan base-package="app07a.formatter" />

    <mvc:annotation-driven conversion-service="conversionService" />

    <mvc:resources mapping="/css/**" location="/css/" />
    <mvc:resources mapping="/*.html" location="/" />

    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean>
    
27     <bean id="messageSource" 
28             class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
29         <property name="basename" value="/WEB-INF/resource/messages" />
30     </bean>
    
    <bean id="conversionService"
        class="org.springframework.format.support.FormattingConversionServiceFactoryBean">
        <property name="formatters">
            <set>
                <bean class="app07a.formatter.DateFormatter">
                    <constructor-arg type="java.lang.String" value="MM-dd-yyyy" />
                </bean>
            </set>
        </property>
    </bean>
</beans>

message.properties文件

productname.required.product.name=Please enter a product name
price.required=Please enter a price
productiondate.required=Please enter a production date
productiondate.invalid=Invalid production date. Please ensure the production date is not later than today.

Controller

package app07a.controller;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.validation.FieldError;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;

import app07a.domain.Product;
import app07a.validator.ProductValidator;

@Controller
public class ProductController {

    private static final Log logger = LogFactory
            .getLog(ProductController.class);

    @RequestMapping(value = "/product_input")
    public String inputProduct(Model model) {
        model.addAttribute("product", new Product());
        return "ProductForm";
    }

    @RequestMapping(value = "/product_save")
    public String saveProduct(@ModelAttribute Product product,
            BindingResult bindingResult, Model model) {
        logger.info("product_save");
        System.out.println("prod save");
        ProductValidator productValidator = new ProductValidator();
        productValidator.validate(product, bindingResult);

        if (bindingResult.hasErrors()) {
            FieldError fieldError = bindingResult.getFieldError();
            logger.info("Code:" + fieldError.getCode() + ", field:"
                    + fieldError.getField());

            return "ProductForm";
        }

        // save product here

        model.addAttribute("product", product);
        return "ProductDetails";
    }
}

测试验证器

http://localhost:8080/app07a/product_input