Spring系列（@FactoryBean注解用法介绍） _FactoryBean

弱龄寄事外，委怀在琴书。这篇文章主要讲述Spring系列：@FactoryBean注解用法介绍相关的知识，希望能为你提供帮助。
?今天给大家介绍@FactoryBean注解用法，希望对大家能有所帮助！?

?1、@FactoryBean注解介绍??FactoryBean是实现了FactoryBean< T> 接口的Bean，可以该Bean的ID从BeanFactory中获取的实际上是FactoryBean中getObject()方法返回的实例对象，而并不是直接FactoryBean本身，想要获取FactoryBean对象本身，可以在id前面加一个& 符号来获取。?
?BeanFactory部分代码：?
?说明：String FACTORY_BEAN_PREFIX = "& " ，& 符号表示要获取FactoryBean本身?

package org.springframework.beans.factory;

import org.springframework.beans.BeansException;
import org.springframework.core.ResolvableType;
import org.springframework.lang.Nullable;

public interface BeanFactory
String FACTORY_BEAN_PREFIX = "& ";

?2、@FactoryBean的源码内容如下：??Spring3.0版本之后，FactoryBean开始支持泛型，即接口声明改为FactoryBean< T> 的形式?

package org.springframework.beans.factory;

import org.springframework.lang.Nullable;

public interface FactoryBean< T>
String OBJECT_TYPE_ATTRIBUTE = "factoryBeanObjectType";

@Nullable
T getObject() throws Exception;

@Nullable
Class< ?> getObjectType();

default boolean isSingleton()
return true;

【Spring系列（@FactoryBean注解用法介绍）】?实现FactoryBean< T> 接口有一下三个方法?

?getObject:获取bean对应的实例对象?
?getObjectType:获取factoryBean获取到的实例类型?
?isSingleton:factoryBean创建的实例是否是单实例?

?3、用法示例??3.1 新建Book.java?

package com.spring.bean;

public class Book
private String bookName;
private String bookType;
private double price;

public Book(String bookName, String bookType, double price)
this.bookName = bookName;
this.bookType = bookType;
this.price = price;

public String getBookName()
return bookName;

public void setBookName(String bookName)
this.bookName = bookName;

public String getBookType()
return bookType;

public void setBookType(String bookType)
this.bookType = bookType;

public double getPrice()
return price;

public void setPrice(double price)
this.price = price;

@Override
public String toString()
return "Book" +
"bookName=" + bookName + \\ +
", bookType=" + bookType + \\ +
", price=" + price +
;

?3.2 新建BookFactoryBean.java?

package com.spring.bean;

import org.springframework.beans.factory.FactoryBean;

public class BookFactoryBean implements FactoryBean< Book>
public BookFactoryBean factoryBeanVO()
return new BookFactoryBean();

public Book getObject() throws Exception
return new Book("红楼梦", "中国名著", 88);

public Class< ?> getObjectType()
return Book.class;

public boolean isSingleton()
return true;

?3.3 FactoryBeanConfig.java?

package com.spring.config;

import com.spring.bean.BookFactoryBean;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class FactoryBeanConfig
@Bean
public BookFactoryBean bookFactoryBean()

return new BookFactoryBean();

?3.4 TestFactoryBean.java?

package com.spring.test;

import com.spring.config.FactoryBeanConfig;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class TestFactoryBean

public static void main(String[] args)
AnnotationConfigApplicationContext annotationContext = new AnnotationConfigApplicationContext(FactoryBeanConfig.class);
// 获取工厂类的bean
Object bookFactoryBean = annotationContext.getBean("bookFactoryBean");
System.out.println(bookFactoryBean.getClass());
// 输出结果： class com.spring.bean.Book
//获取FactoryBean 本身加 & 符号
Object bookFactoryBean1 = annotationContext.getBean("& bookFactoryBean");
System.out.println(bookFactoryBean1.getClass());
// 输出结果： class com.spring.bean.BookFactoryBean

?4、@FactoryBean应用场景?