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自定义类型转换器_细节
=====================

1 通过依赖注入解耦合

                    _____________________________________________
                   |                                             |
                   v                                             |
public class StringToDate implements Converter<String, Date> {   |
    @Override      |___________________________                  |
    public Date convert(String s) {            |                 |
        Date date = null;                      |依赖             |注入
                                               |                 |
        try {                                  v                 |
            date =  new SimpleDateFormat("yyyy-MM-dd").parse(s); |
        }                                      |_________________|
        catch (ParseException e) {
            e.printStackTrace();
        }

        return date;
    }
}

/src/main/java/cn/tedu/injection/StringToDate.java：

public class StringToDate implements Converter<String, Date> {
    private String pattern;

    public void setPattern(String pattern) {
        this.pattern = pattern;
    }

    @Override
    public Date convert(String s) {
        Date date = null;

        try {
            date =  new SimpleDateFormat(pattern).parse(s);
        }
        catch (ParseException e) {
            e.printStackTrace();
        }

        return date;
    }
}

/src/main/resources/applicationContext.xml：

<bean id="stringToDate" class="cn.tedu.injection.StringToDate">
    <property name="pattern" value="yyyy-MM-dd"/>
</bean>

例程：Injection

2 类型转换器对象的id是专有的

             不能随便写
                  |
                  v
<bean id="conversionService"
      class="org.springframework.context.support.ConversionServiceFactoryBean">
    ...
</bean>

3 内置日期类型转换器

Spring内部其实是有String-Date类型转换器的，只是它只能转换"yyyy/MM/dd"格式的日期。

/src/main/resources/applicationContext.xml：

<bean id="user" class="cn.tedu.injection.User">
    <property name="id" value="1001"/>
    <property name="birthday" value="2018/09/10"/>
</bean>

例程：Injection