BeanFactory和FactoryBean

　　BeanFactory和FactoryBean是spring里的两个接口,区分他们关键看后面的单词，一个是生产Bean的工厂，一个工厂Bean。前者是生产spring整个IOC的工厂，所以它可以包含后者；后者仅仅作为特定bean的工厂，服务对象片面，主要用于代理，实现AOP用，比如CacheProxyFactoryBean。先看下这两个接口，再看下一个实例的代码：

　　BeanFactory：

public interface BeanFactory {
    String FACTORY_BEAN_PREFIX = "&";

    Object getBean(String arg0) throws BeansException;

    <T> T getBean(String arg0, Class<T> arg1) throws BeansException;

    <T> T getBean(Class<T> arg0) throws BeansException;

    Object getBean(String arg0, Object... arg1) throws BeansException;

    boolean containsBean(String arg0);

    boolean isSingleton(String arg0) throws NoSuchBeanDefinitionException;

    boolean isPrototype(String arg0) throws NoSuchBeanDefinitionException;

    boolean isTypeMatch(String arg0, Class<?> arg1) throws NoSuchBeanDefinitionException;

    Class<?> getType(String arg0) throws NoSuchBeanDefinitionException;

    String[] getAliases(String arg0);
}

　　FactoryBean：

public interface FactoryBean<T> {
    T getObject() throws Exception;

    Class<?> getObjectType();

    boolean isSingleton();
}

　　实例代码：

package spitter;

import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;

import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;

public class Spitter {
    private long id;

    @NotNull
    @Size(min = 5, max = 16)
    private String firstName;

    @NotNull
    @Size(min = 5, max = 25)
    private String lastName;

    @NotNull
    @Size(min = 20, max = 30)
    private String username;

    @NotNull
    @Size(min = 2, max = 30)
    private String password;

    public Spitter(String firstName, String lastName, String username, String password) {
        this(0L, firstName, lastName, username, password);

    }

    public Spitter(long id, String firstName, String lastName, String username, String password) {
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
        this.username = username;
        this.password = password;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return firstName + username + lastName + ", " + password;
    }

package spitter;

import org.springframework.beans.factory.FactoryBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpitterFactoryBean implements FactoryBean<Spitter> {

    @Override
    public Spitter getObject() throws Exception {
        return new Spitter("Wu", "Feng", "Lin", "123456");
    }

    @Override
    public Class<?> getObjectType() {
        return Spitter.class;
    }

    @Override
    public boolean isSingleton() {
        return true;
    }

    public static void main(String[] args) throws Exception {
        // 读取配置文件，加载ioc容器，ApplicationContext的顶层接口就是BeanFactory
        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        
        // getBean也是BeanFactory里的接口
        Spitter spitter = app.getBean("spitter", Spitter.class);
        System.out.printf("BeanFactory 生成的实例：%s
", spitter.toString());
        System.out.printf("BeanFactory其他方法，是否包含bean：%b, 是否单例：%b
",app.containsBean("spitter"),app.isSingleton("spitter"));
        
        // 直接new实例化FactoryBean
        SpitterFactoryBean spitterFactory = new SpitterFactoryBean();
        spitter = spitterFactory.getObject();
        System.out.printf("FactoryBean 生成的实例：%s
", spitter.toString());
        System.out.printf("FactoryBean其他方法，bean加载的类型：%s, 是否单例：%b
",spitterFactory.getObjectType(),spitterFactory.isSingleton());
        
        // 通过BeanFactory实例化FactoryBean
        spitterFactory = (SpitterFactoryBean)app.getBean("&spitterFactoryBean");
        System.out.printf("BeanFactory 生成FactoryBean，FactoryBean 生成的实例：%s
", spitter.toString());
        
    }

}

applicationContext.xml：必须放在webappsWEB-INFclasses目录下

<?xml version="1.0" encoding="UTF-8"?>
<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.xsd">
    <bean id="spitter" class="spitter.Spitter">
        <constructor-arg value="Wu" />
        <constructor-arg value="Shu" />
        <constructor-arg value="Man" />
        <constructor-arg value="654321" />
    </bean>

    <bean id="spitterFactoryBean" class="spitter.SpitterFactoryBean" />
</beans>

　　运行结果：

三月 30, 2017 12:08:42 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@2328c243: startup date [Thu Mar 30 00:08:42 CST 2017]; root of context hierarchy
三月 30, 2017 12:08:43 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [applicationContext.xml]
BeanFactory 生成的实例：WuManShu, 654321
BeanFactory其他方法，是否包含bean：true, 是否单例：true
FactoryBean 生成的实例：WuLinFeng, 123456
FactoryBean其他方法，bean加载的类型：class spitter.Spitter, 是否单例：true
BeanFactory 生成FactoryBean，FactoryBean 生成的实例：WuLinFeng, 123456