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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