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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