Spring中的转换器：Converter

配置spring的配置文件：

 1 <bean id="conversionService"
 2         class="org.springframework.context.support.ConversionServiceFactoryBean">
 3         <property name="converters">
 4             <list>
 5                 <bean class="app06a.converter.StringToDateConverter">
 6                     <constructor-arg type="java.lang.String" value="MM-dd-yyyy"/>
 7                 </bean>
 8             </list>
 9         </property>
10     </bean>
11     <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。

 1 public class StringToDateConverter implements Converter<String,Date>{
 2     private String datePattern;
 3     public StringToDateConverter(String datePattern){
 4         this.datePattern=datePattern;
 5         System.out.println("instiating"+datePattern);
 6     }
 7     @Override
 8     public Date convert(String s) {
 9         SimpleDateFormat dateformat=new SimpleDateFormat();
10         dateformat.setLenient(false);
11         try {
12             return dateformat.parse(s);
13         } catch (ParseException e) {
14             throw new IllegalArgumentException("invailed date"+datePattern+"\"");
15         }
16     }
17 }

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：

 1 @RequestMapping(value="/employee_input")
 2     public String inputEmployee(Model model){
 3         model.addAttribute("employee",new Employee());
 4         return "EmployeeForm";
 5     }
 6
 7     @RequestMapping(value="/employee_save")
 8     public String saveEmployee(@ModelAttribute Employee employee,BindingResult bindresult,Model model){
 9         if(bindresult.hasErrors()){
10             FieldError fielderror=bindresult.getFieldError();
11             return "EmployeeForm";
12         }
13         model.addAttribute("employee",employee);
14         return "EmployeeDetails";
15     }

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