這一個Spring例子向您展示如何為bean屬性注入一個“日期”。
package com.xuhuhu.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配置檔
<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.xuhuhu.common.Customer"> <property name="date" value="2015-12-31" /> </bean> </beans>
執行-運行程式輸出
package com.xuhuhu.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
聲明一個dateFormat bean，在“customer” Bean，引用 “dateFormat” bean作為一個工廠bean。該工廠方法將調用SimpleDateFormat.parse()自動轉換成字串Date對象。
<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.xuhuhu.common.Customer"> <property name="date"> <bean factory-bean="dateFormat" factory-method="parse"> <constructor-arg value="2015-12-31" /> </bean> </property> </bean> </beans>
2. CustomDateEditor
聲明一個 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>
並聲明另一個“CustomEditorConfigurer”，使 Spring轉換 bean 屬性，其類型為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配置檔的完整例子(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.xuhuhu.common.Customer"> <property name="date" value="2015-12-31" /> </bean> </beans>