Spring注入日期到bean屬性-CustomDateEditor

這一個Spring例子向您展示如何為bean屬性注入一個「日期」。

package com.tw511.common;

import java.util.Date;

public class Customer {

	Date date;

	public Date getDate() {
		return date;
	}

	public void setDate(Date date) {
		this.date = date;
	}

	@Override
	public String toString() {
		return "Customer [date=" + date + "]";
	}

}

bean組態檔案

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
	http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

	<bean id="customer" class="com.tw511.common.Customer">
		<property name="date" value="2015-12-31" />
	</bean>

</beans>

執行-執行程式輸出

package com.tw511.common;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class App {
	public static void main(String[] args) {
		ApplicationContext context = new ClassPathXmlApplicationContext(
				"SpringBeans.xml");

		Customer cust = (Customer) context.getBean("customer");
		System.out.println(cust);
		
	}
}

可能會遇到如下錯誤資訊：

Caused by: org.springframework.beans.TypeMismatchException: 
	Failed to convert property value of type [java.lang.String] to 
	required type [java.util.Date] for property 'date'; 

nested exception is java.lang.IllegalArgumentException: 
	Cannot convert value of type [java.lang.String] to
	required type [java.util.Date] for property 'date': 
	no matching editors or conversion strategy found

解決辦法

在Spring中，可以通過兩種方式注入日期：

1. Factory bean

宣告一個dateFormat bean，在「customer」 Bean，參照「dateFormat」 bean作為一個工廠bean。該工廠方法將呼叫SimpleDateFormat.parse()自動轉換成字串Date物件。

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
	http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

	<bean id="dateFormat" class="java.text.SimpleDateFormat">
		<constructor-arg value="yyyy-MM-dd" />
	</bean>

	<bean id="customer" class="com.tw511.common.Customer">
		<property name="date">
			<bean factory-bean="dateFormat" factory-method="parse">
				<constructor-arg value="2015-12-31" />
			</bean>
		</property>
	</bean>

</beans>

2. CustomDateEditor

宣告一個 CustomDateEditor 類將字串轉換成 java.util.Date。

<bean id="dateEditor"
	   class="org.springframework.beans.propertyeditors.CustomDateEditor">
	
		<constructor-arg>
			<bean class="java.text.SimpleDateFormat">
				<constructor-arg value="yyyy-MM-dd" />
			</bean>
		</constructor-arg>
		<constructor-arg value="true" />
	</bean>

並宣告另一個「CustomEditorConfigurer」，使 Spring轉換 bean 屬性，其型別為java.util.Date。

<bean class="org.springframework.beans.factory.config.CustomEditorConfigurer">
		<property name="customEditors">
			<map>
				<entry key="java.util.Date">
					<ref local="dateEditor" />
				</entry>
			</map>
		</property>
	</bean>

bean組態檔案的完整例子(applicationContext.xml)。

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
	http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

	<bean id="dateEditor"
		class="org.springframework.beans.propertyeditors.CustomDateEditor">

		<constructor-arg>
			<bean class="java.text.SimpleDateFormat">
				<constructor-arg value="yyyy-MM-dd" />
			</bean>
		</constructor-arg>
		<constructor-arg value="true" />

	</bean>

	<bean class="org.springframework.beans.factory.config.CustomEditorConfigurer">
		<property name="customEditors">
			<map>
				<entry key="java.util.Date">
					<ref local="dateEditor" />
				</entry>
			</map>
		</property>
	</bean>

	<bean id="customer" class="com.tw511.common.Customer">
		<property name="date" value="2015-12-31" />
	</bean>

</beans>

下載程式碼 – http://pan.baidu.com/s/1bxZyfO