java - Spring通过注解在字段中注入(inject)java.util.Date

Question

我学习了 Spring 框架并尝试在 fiel 类中注入(inject) java.util.Date 。

Foo.class

package beans;

    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.stereotype.Component;

    import java.util.Date;

    @Component
    public class Foo {
        @Value("Hello foo")
        private String string;

        @Value("#{T(java.util.Date)}")
        private Date date;

        public String getString() {
            return string;
        }

        public void setString(String string) {
            this.string = string;
        }

        public Date getDate() {
            return date;
        }


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

主类

import beans.Foo;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {

    public static void main(String[] args) {
        ConfigurableApplicationContext ctx = new ClassPathXmlApplicationContext("spring.xml");

        System.out.println(ctx.getBean(Foo.class).getString());
        System.out.println(ctx.getBean(Foo.class).getDate());
    } 
}

spring.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
           http://www.springframework.org/schema/beans
           http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-3.2.xsd"> 
    <context:annotation-config/>
    <context:component-scan base-package="beans"/>
</beans>

异常(exception):

Exception encountered during context initialization - cancelling refresh attempt
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'foo': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private java.util.Date beans.Foo.date; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert value of type 'java.lang.Class' to required type 'java.util.Date'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.Class] to required type [java.util.Date]: no matching editors or conversion strategy found

Answer 1

在 Spring 表达式语言中，#{T(java.util.Date)} 表示对 Date.class 的引用，它与中的 Date 引用不兼容你的 bean 。

如果您想设置诸如系统当前日期之类的内容，您可以尝试

@Value("#{new java.util.Date()}")

甚至是特定日期

@Value("#{new java.text.SimpleDateFormat(\"MM/dd/yyyy\").parse(\"01/01/2018\")}")