Spring中的转换器：Converter

配置spring的配置文件：

 <bean id="conversionService"

         class="org.springframework.context.support.ConversionServiceFactoryBean">

         <property name="converters">

             <list>

                 <bean class="app06a.converter.StringToDateConverter">

                     <constructor-arg type="java.lang.String" value="MM-dd-yyyy"/>

                 </bean>

             </list>

         </property>

     </bean>

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

这样配置好了之后，就可以创建一个Converter的装换器类来写一个转换器的实现。这里我们写的转换器是把String类型转换为Date类型的。日期格式为value后面的。

 public class StringToDateConverter implements Converter<String,Date>{

     private String datePattern;

     public StringToDateConverter(String datePattern){

         this.datePattern=datePattern;

         System.out.println("instiating"+datePattern);

     }

     @Override

     public Date convert(String s) {

         SimpleDateFormat dateformat=new SimpleDateFormat();

         dateformat.setLenient(false);

         try {

             return dateformat.parse(s);

         } catch (ParseException e) {

             throw new IllegalArgumentException("invailed date"+datePattern+"\"");

         }

     }

 }

然后实现了Converer<S,T>接口。

这样，若是日期输入错误，则会返回之前输入的页面，页面上也会出现提示：

 @RequestMapping(value="/employee_input")

     public String inputEmployee(Model model){

         model.addAttribute("employee",new Employee());

         return "EmployeeForm";

     }

     @RequestMapping(value="/employee_save")

     public String saveEmployee(@ModelAttribute Employee employee,BindingResult bindresult,Model model){

         if(bindresult.hasErrors()){

             FieldError fielderror=bindresult.getFieldError();

             return "EmployeeForm";

         }

         model.addAttribute("employee",employee);

         return "EmployeeDetails";

     }

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