Spring：Spring配置Bean
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在Spring的IOC容器里配置Bean
配置Bean形式：基于xml文件方式、基于注解的方式
在xml文件中通过bean节点配置bean:
<?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 name="helloSpring" class="com.dx.spring.beans.HelloSpring"> <property name="name" value="Spring"></property> </bean> </beans>
参考：《Spring（二）：Spring框架&Hello Spring》中配置过程
id:Bean的名称
1）在IOC容器中必须是唯一的；
2）若id没有指定，Spring会自动将全系nag定型为类名作为Bean的名字；
3）id可以指定多个名字，名字之间可用逗号、分号、或空格分隔。
Bean的配置方式：
1）通过全类名（反射实现，此时要求该bean类拥有一个无参数构造器）、
2）通过工厂方法（静态工厂方法&实例工厂方法，参考：《Spring（十三）：使用工厂方法来配置Bean的两种方式（静态工厂方法&实例工厂方法）》）、
3）FactoryBean（参考：《Spring（十四）：使用FactoryBean配置Bean》）
4）@Configuration注解的配置类中注册bean，具体如下：
package test; public class User { private Integer id; private String name; 。。。 } // 定义配置Bean配置类 import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configuration public class ApplicationConfigBean { @Bean public User getUser() { return new User(); } } // 测试类 import org.springframework.context.ApplicationContext; import org.springframework.context.annotation.AnnotationConfigApplicationContext; public class App { public static void main(String[] args) { ApplicationContext ctx = new AnnotationConfigApplicationContext(ApplicationConfigBean.class); System.out.println(ctx.getBean(User.class)); } }
IOC容器BeanFactory&ApplicationContext概述
Spring容器
1）在Spring IOC容器读取Bean配置创建Bean实例之前，必须对它进行实例化。只有在容器实例化后，才可以从IOC容器里获取Bean实例并使用。
2）Spring提供了两种类型IOC容器实现
---BeanFactory：IOC容器的基本实现。BeanFactory是Spring框架的基础设施，面向Spring本身。
---ApplicationContext：提供了更多的高级属性，是BeanFactory的子接口。ApplicationContext面向使用Spring框架的开发者，几乎所有的应用场合都直接使用ApplicationContext，而非底层的BeanFactory。
备注：
1）无论使用两种方式的哪一种，配置文件是相同的。
2）如何却别ApplicatinContext是BeanFactory的子接口：
ApplicatinContext的类定义：
// Compiled from ApplicationContext.java (version 1.8 : 52.0, no super bit) public abstract interface org.springframework.context.ApplicationContext
extends org.springframework.core.env.EnvironmentCapable,
org.springframework.beans.factory.ListableBeanFactory,
org.springframework.beans.factory.HierarchicalBeanFactory,
org.springframework.context.MessageSource,
org.springframework.context.ApplicationEventPublisher,
org.springframework.core.io.support.ResourcePatternResolver { // Method descriptor #10 ()Ljava/lang/String; @org.springframework.lang.Nullable public abstract java.lang.String getId(); // Method descriptor #10 ()Ljava/lang/String; public abstract java.lang.String getApplicationName(); // Method descriptor #10 ()Ljava/lang/String; public abstract java.lang.String getDisplayName(); // Method descriptor #16 ()J public abstract long getStartupDate(); // Method descriptor #18 ()Lorg/springframework/context/ApplicationContext; @org.springframework.lang.Nullable public abstract org.springframework.context.ApplicationContext getParent(); // Method descriptor #20 ()Lorg/springframework/beans/factory/config/AutowireCapableBeanFactory; public abstract org.springframework.beans.factory.config.AutowireCapableBeanFactory getAutowireCapableBeanFactory() throws java.lang.IllegalStateException; }
从上边我们知道ApplicationContext是继承了org.springframework.beans.factory.ListableBeanFactory，org.springframework.beans.factory.HierarchicalBeanFactory接口，而这两个接口都是继承了org.springframework.beans.factory.BeanFactory接口。
public interface BeanFactory { String FACTORY_BEAN_PREFIX = "&"; Object getBean(String name) throws BeansException; <T> T getBean(String name, @Nullable Class<T> requiredType) throws BeansException; Object getBean(String name, Object... args) throws BeansException; <T> T getBean(Class<T> requiredType) throws BeansException; <T> T getBean(Class<T> requiredType, Object... args) throws BeansException; boolean containsBean(String name); boolean isSingleton(String name) throws NoSuchBeanDefinitionException; boolean isPrototype(String name) throws NoSuchBeanDefinitionException; boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException; boolean isTypeMatch(String name, @Nullable Class<?> typeToMatch) throws NoSuchBeanDefinitionException; @Nullable Class<?> getType(String name) throws NoSuchBeanDefinitionException; String[] getAliases(String name); }
因此，说ApplicationContext是BeanFactory的子接口类。
ApplicaionContext
ApplicationContext的主要实现类：
---ClassPathXmlApplicationContext：从类路径下加载配置文件
---FileSystemXmlApplicationContext：从文件系统中加载配置文件。
ConfigurableApplicationContext扩展与ApplicationContext，新增加两个主要的方法：refresh()和close()，让ApplicationContext具有启动、刷新和关闭上下文的能力。
// Compiled from ConfigurableApplicationContext.java (version 1.8 : 52.0, no super bit) public abstract interface org.springframework.context.ConfigurableApplicationContext extends org.springframework.context.ApplicationContext, org.springframework.context.Lifecycle, java.io.Closeable { // Field descriptor #8 Ljava/lang/String; public static final java.lang.String CONFIG_LOCATION_DELIMITERS = ",; \\t\\n"; // Field descriptor #8 Ljava/lang/String; public static final java.lang.String CONVERSION_SERVICE_BEAN_NAME = "conversionService"; // Field descriptor #8 Ljava/lang/String; public static final java.lang.String LOAD_TIME_WEAVER_BEAN_NAME = "loadTimeWeaver"; // Field descriptor #8 Ljava/lang/String; public static final java.lang.String ENVIRONMENT_BEAN_NAME = "environment"; // Field descriptor #8 Ljava/lang/String; public static final java.lang.String SYSTEM_PROPERTIES_BEAN_NAME = "systemProperties"; // Field descriptor #8 Ljava/lang/String; public static final java.lang.String SYSTEM_ENVIRONMENT_BEAN_NAME = "systemEnvironment"; // Method descriptor #22 (Ljava/lang/String;)V public abstract void setId(java.lang.String arg0); // Method descriptor #24 (Lorg/springframework/context/ApplicationContext;)V public abstract void setParent(@org.springframework.lang.Nullable org.springframework.context.ApplicationContext arg0); // Method descriptor #28 (Lorg/springframework/core/env/ConfigurableEnvironment;)V public abstract void setEnvironment(org.springframework.core.env.ConfigurableEnvironment arg0); // Method descriptor #30 ()Lorg/springframework/core/env/ConfigurableEnvironment; public abstract org.springframework.core.env.ConfigurableEnvironment getEnvironment(); // Method descriptor #32 (Lorg/springframework/beans/factory/config/BeanFactoryPostProcessor;)V public abstract void addBeanFactoryPostProcessor(org.springframework.beans.factory.config.BeanFactoryPostProcessor arg0); // Method descriptor #34 (Lorg/springframework/context/ApplicationListener;)V // Signature: (Lorg/springframework/context/ApplicationListener<*>;)V public abstract void addApplicationListener(org.springframework.context.ApplicationListener arg0); // Method descriptor #38 (Lorg/springframework/core/io/ProtocolResolver;)V public abstract void addProtocolResolver(org.springframework.core.io.ProtocolResolver arg0); // Method descriptor #40 ()V public abstract void refresh() throws org.springframework.beans.BeansException, java.lang.IllegalStateException; // Method descriptor #40 ()V public abstract void registerShutdownHook(); // Method descriptor #40 ()V public abstract void close(); // Method descriptor #47 ()Z public abstract boolean isActive(); // Method descriptor #49 ()Lorg/springframework/beans/factory/config/ConfigurableListableBeanFactory; public abstract org.springframework.beans.factory.config.ConfigurableListableBeanFactory getBeanFactory() throws java.lang.IllegalStateException; // Method descriptor #50 ()Lorg/springframework/core/env/Environment; // Stack: 1, Locals: 1 public bridge synthetic org.springframework.core.env.Environment getEnvironment(); 0 aload_0 [this] 1 invokeinterface org.springframework.context.ConfigurableApplicationContext.getEnvironment() : org.springframework.core.env.ConfigurableEnvironment [1] [nargs: 1] 6 areturn Line numbers: [pc: 0, line: 43] Local variable table: [pc: 0, pc: 7] local: this index: 0 type: org.springframework.context.ConfigurableApplicationContext }
ApplicationContext在初始化上下文时就实例化所有单例的Bean。
WebApplicationContext是专门为WEB应用而准备的，它允许从相对于WEB根目录的路径中完成初始化工作。
依赖注入的方式：
1）属性注入（set方法注入）；
package com.dx.spring.beans; public class HelloSpring { private String name; public HelloSpring() { } public void setName(String name) { this.name = name; } public void sayHello() { System.out.println("Hello " + this.name); } }
setName方法注入：
<bean name="helloSpring" class="com.dx.spring.beans.HelloSpring"> <property name="name" value="Spring"></property> </bean>
2）构造函数注入；
a）通过构造方法注入Bean的属性值或依赖的对象，它保证了Bean实例在实例化后就可以使用。
b）构造器注入在<constructor-arg>元素里声明属性，<constructor-arg>中没有name属性。
<bean name="car" class="com.dx.spring.beans.Car"> <constructor-arg value="AUDI" index="0"></constructor-arg> <constructor-arg value="Shanghai" index="1"></constructor-arg> <constructor-arg value="400000" type="double"></constructor-arg> </bean> <bean name="car2" class="com.dx.spring.beans.Car"> <constructor-arg value="BMW" type="java.lang.String"></constructor-arg> <constructor-arg value="Shanghai" type="java.lang.String"></constructor-arg> <constructor-arg value="260" type="int"></constructor-arg> </bean>
Car.java
package com.dx.spring.beans; public class Car { private String brand; private String corp; private double price; private int maxSpeed; public Car(String brand, String corp, double price) { super(); this.brand = brand; this.corp = corp; this.price = price; } public Car(String brand, String corp, int maxSpeed) { super(); this.brand = brand; this.corp = corp; this.maxSpeed = maxSpeed; } @Override public String toString() { return "Car [brand=" + brand + ", corp=" + corp + ", price=" + price + ", maxSpeed=" + maxSpeed + "]"; } }
client.java
public static void main(String[] args) { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); HelloSpring helloSpring = (HelloSpring) applicationContext.getBean("helloSpring"); Car car = (Car) applicationContext.getBean("car"); Car car2 = (Car) applicationContext.getBean("car2"); System.out.println(car); System.out.println(car2); }
输出信息：
Car [brand=AUDI, corp=Shanghai, price=400000.0, maxSpeed=0] Car [brand=BMW, corp=Shanghai, price=0.0, maxSpeed=260]
3）工厂方法注入
不推荐、也不常用
注入属性值细节
1）字面值
字面值：可用字符串表示的值，可以通过<value>元素标签或value属性进行注入。
基本数据类型及封装类、String等类型都可以采用字面值注入的方式
若字面值中包含特殊字符，可以使用<![CDATA[]]>把字面值包裹起来。
Person.java
package com.dx.spring.beans; public class Person { private String name; private String age; private Car car; public Person(String name, String age, Car car) { super(); this.name = name; this.age = age; this.car = car; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getAge() { return age; } public void setAge(String age) { this.age = age; } public Car getCar() { return car; } public void setCar(Car car) { this.car = car; } @Override public String toString() { return "Person [name=" + name + ", age=" + age + ", car=" + car + "]"; } }
<bean name="car2" class="com.dx.spring.beans.Car"> <constructor-arg value="BMW" type="java.lang.String"></constructor-arg> <constructor-arg type="java.lang.String"> <value><![CDATA[<Shanghai>]]></value> </constructor-arg> <constructor-arg type="int"> <value>260</value> </constructor-arg> </bean>
2）引用其它Bean
组成应用程序的Bean机场需要相互协作已完成应用程序的功能，需要使用Bean能够相互访问，就必须在Bean配置文件中指定对Bean的引用
在Bean的配置文件中，可以通过<ref>元素或者ref属性为bean的属性或，构造器参数指定对bean的引用。
也可以在属性或构造器里包含Bean的声明，这样的Bean成为内部Bean。
3）注入参数详解：null值和级联属性
可以使用专用的<null/>元素标签为bean的字符串或其它对象类型的属性注入null值。
<bean id="person3" class="com.dx.spring.beans.Person"> <constructor-arg value="Lisi"></constructor-arg> <constructor-arg value="25"></constructor-arg> <constructor-arg name="car"> <null/> </constructor-arg> </bean>
和struts、hibernate等框架一样，spring支持级联属性的配置。
<bean id="person" class="com.dx.spring.beans.Person"> <constructor-arg value="Zhangsan"></constructor-arg> <constructor-arg value="24"></constructor-arg> <constructor-arg ref="car"></constructor-arg> <property name="car.maxSpeed" value="260"></property> </bean>
注意：
1)上边代码必须要要求先初始化car，否则直接给car.maxSpeed赋值会抛出异常与struts2不同点。
2)需要在car中实现setMaxSpeed方法。
public void setMaxSpeed(int maxSpeed) { this.maxSpeed = maxSpeed; }
4）集合属性
在Spring中可以通过一组内置的xml标签（例如：<list>，<set>，<map>）来配置集合属性。
4.1)配置java.util.List类型的属性，需要指定<list>标签，在标签里包含一些元素。这些标签可以通过<value>指定简单的常量值，通过<ref>指定对其它Bean的引用，通过<bean>指定内置bean定义。通过<null/>指定空元素。甚至可以内嵌其他集合。
applicationContext.xml
<bean name="car" class="com.dx.spring.beans.Car"> <constructor-arg value="AUDI" index="0"></constructor-arg> <constructor-arg value="Shanghai" index="1"></constructor-arg> <constructor-arg value="400000" type="double"></constructor-arg> </bean> <bean name="car2" class="com.dx.spring.beans.Car"> <constructor-arg value="BMW" type="java.lang.String"></constructor-arg> <constructor-arg type="java.lang.String"> <value><![CDATA[<Shanghai>]]></value> </constructor-arg> <constructor-arg type="int"> <value>260</value> </constructor-arg> </bean> <bean id="person4" class="com.dx.spring.beans.collections.Person"> <property name="name" value="Nike"></property> <property name="age" value="25"></property> <property name="cars"> <list> <ref bean="car" /> <ref bean="car2" /> </list> </property> </bean>
client.java
public static void main(String[] args) { ApplicationContext cxt = new ClassPathXmlApplicationContext("applicationContext.xml"); Person person = (Person) cxt.getBean("person4"); System.out.println(person); }
Person.java
package com.dx.spring.beans.collections; import java.util.List; import com.dx.spring.beans.Car; public class Person { private String name; private int age; private List<Car> cars; public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public List<Car> getCars() { return cars; } public void setCars(List<Car> cars) { this.cars = cars; } @Override public String toString() { return "Person [name=" + name + ", age=" + age + ", cars=" + cars + "]"; } }
打印结果：
Person [name=Nike, age=25, cars=[Car [brand=AUDI, corp=Shanghai, price=400000.0, maxSpeed=260], Car [brand=BMW, corp=<Shanghai>, price=0.0, maxSpeed=260]]]
4.2)数组的定义和List一样，都可以使用<list>
修改Person.java为：
public Car[] getCars() { return cars; } public void setCars(Car[] cars) { this.cars = cars; } @Override public String toString() { String carsStr = ""; for (Car car : cars) carsStr += car.toString() + ","; return "Person [name=" + name + ", age=" + age + ", cars=[" + carsStr + "]]"; }
applicationContext.xml不变，client.java也不变，打印结果：
Person [name=Nike, age=25, cars=[Car [brand=AUDI, corp=Shanghai, price=400000.0, maxSpeed=260],Car [brand=BMW, corp=<Shanghai>, price=0.0, maxSpeed=260],]]
4.3)配置java.util.Set需要使用<set>标签，定义元素的方法与List一样。
修改Person.car属性类型：
private Set<Car> cars; public Set<Car> getCars() { return cars; } public void setCars(Set<Car> cars) { this.cars = cars; } @Override public String toString() { return "Person [name=" + name + ", age=" + age + ", cars=" + cars+ "]"; }
修改applicationContext.xml
<bean id="person4" class="com.dx.spring.beans.collections.Person"> <property name="name" value="Nike"></property> <property name="age" value="25"></property> <property name="cars"> <set> <ref bean="car" /> <ref bean="car2" /> </set> </property> </bean>
client.java不变，打印结果：
Person [name=Nike, age=25, cars=[Car [brand=AUDI, corp=Shanghai, price=400000.0, maxSpeed=260], Car [brand=BMW, corp=<Shanghai>, price=0.0, maxSpeed=260]]]
4.4)java.util.Map通过<map>标签定义，<map>标签里可以使用多个<en 以上是关于Spring：Spring配置Bean的主要内容，如果未能解决你的问题，请参考以下文章