Day24 SpringMVC date format conversion***

SpringMVC parameter binding-date format conversion

1. SpringMVC does not support the conversion of date strings on the page to Date in the background by default

• Front Form

  出生日期<input type="date" name="birthday2"/><br/>

• Correspondence between entity class and form submission data (string)
  

2. There are two ways to solve it

(1) Use annotations to achieve

Annotation date type converter
@DateTimeFormat("格式")
Just modify the birthday2 date attribute and add a @DateTimeFormat("format")

public class Person {
    
    
    private int id;
    private String username;
    private String password;
    private String city;
    private Birthday birthday;
    @DateTimeFormat(pattern ="yyyy-MM-dd")
    private Date birthday2;
}

How to write the format behind the comment? Write according to the actual data sent by the request. For
example: "2020-10-14" is written as "yyyy-MM-dd"

(2) The second kind of self-write conversion class, configure to springMVC (global date converter)

The implementation steps of writing a custom date type converter:

1. Write a custom converter to implement the Converter rewrite method and convert

import org.springframework.core.convert.converter.Converter;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

//1:将页面上提交的日期字符串，转成Date对象
public class DateTimeFormatConverter implements Converter<String, Date> {
    
    
    public Date convert(String s) {
    
    
        System.out.println("convert "+s);
        //2:转换器
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date date = null;
        try {
    
    
            date = sdf.parse(s);//2020-10-14
        } catch (ParseException e) {
    
    
            e.printStackTrace();
        }
        return date;
    }
}

2. Configure the conversion factory in springmvc.xml and set our converter to the converters collection

<!--注册转换器，并注入自定义的转换器-->
    <bean id="formattingConversionService" class="org.springframework.format.support.FormattingConversionServiceFactoryBean">
        <property name="converters">
            <set>
                <!--配置自己自定义的转换器-->
                <bean id="dateTimeFormatConverter" class="cn.cyl.util.DateTimeFormatConverter"></bean>
            </set>
        </property>
    </bean>

3. Mount the conversion factory object to the processor adapter (mount to the annotation driver)

  <!--springmvc注解驱动标签，引入转换器-->
  <mvc:annotation-driven conversion-service="formattingConversionService"/>

3. Conversion of background date data to page

Background Date data

		List<Person> list = new ArrayList<Person>();

        list.add(new Person(1,"jack","123456","北京",new Birthday(1998,1,1),new Date()));
        list.add(new Person(2,"rose","123456","changsha",new Birthday(1998,2,2),new Date()));

Front Form

    <c:forEach items="${list}" var="item" >
    	<tr>
   	 		<%--此格式输出的是系统日期格式--%>
			<td>${item.birthday2}</td>
		</tr>
    </c:forEach>

Front display

• Add date formatting tags to the foreground form

(1) Import tags

<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt"%>

(2) Call date formatting tag

<fmt:formatDate value="${item.birthday2}" pattern="yyyy年MM月dd日"/>

Front Form

<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>

    <c:forEach items="${list}" var="item" >
    	<tr>
   	 		<%--调用日期格式化标签--%>
            <td><fmt:formatDate value="${item.birthday2}" pattern="yyyy年MM月dd日"/></td>
		</tr>
    </c:forEach>

Front display