Java Spring 自动装配 Java Spring 自动装配如果被注入的属性类型是Bean引用的话，那么可以在<bean>标签中使用autowire属性去配置自动注入方式，属性值有两个byName：通过属性名自动装配，即去匹配setXxx与id="xxx"(name="xxx")是否一致；byType：通过Bean的类型从容器中匹配，匹配出多个相同Bean类型，报错。beans.xml<bean class="org.example.UserDaoImpl" id="userDao"/> <bean class="org.example.UserServiceImpl" id="userService" autowire="byName"/> <bean class="org.example.UserServiceImpl" id="userService1" autowire="byType"/>UserServicepublic interface UserService { public void show(); }UserServiceImplpublic class UserServiceImpl implements UserService { private UserDao userDao; public void setUserDao(UserDao userDao){ this.userDao = userDao; } @Override public void show() { System.out.println(userDao); } }主函数调用public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); ((UserService) applicationContext.getBean("userService")).show(); ((UserService) applicationContext.getBean("userService1")).show(); }执行结果org.example.UserDaoImpl@1f0f1111 org.example.UserDaoImpl@1f0f1111如果xml文件自动装配中有多个同类型的bean容器将会报错例如：<bean class="org.example.UserDaoImpl" id="userDao"/> <bean class="org.example.UserDaoImpl" id="userDao1"/> <bean class="org.example.UserServiceImpl" id="userService" autowire="byName"/> <bean class="org.example.UserServiceImpl" id="userService1" autowire="byType"/>IDEA报错提示无法自动装配。存在多个 'UserDao' 类型的 Bean。Bean: userDao1,userDao。属性: 'userDao'运行结果提示警告: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userService1' defined in class path resource [beans.xml]: Unsatisfied dependency expressed through bean property 'userDao'; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'org.example.UserDao' available: expected single matching bean but found 2: userDao,userDao1 Exception in thread "main" org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userService1' defined in class path resource [beans.xml]: Unsatisfied dependency expressed through bean property 'userDao'; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'org.example.UserDao' available: expected single matching bean but found 2: userDao,userDao1

Java 基于xml的Spring应用 Java 基于xml的Spring应用1.SpringBean 的配置解析Spring开发中主要是对Bean的配置，Bean的常用配置一览如下： 1.Bean的基础配置配置UserDaoImpl由Spring容器负责管理<bean id="userDao" class="org.example.UserDaoImpl"></bean>此时存储到Spring容器（singleObjects单例池）中的Bean的beanName是userDao，值是UserDaoImpl对象，可以根据beanName获取Bean实例applicationContext.getBean("userDao")如果不配置id，则Spring会把当前Bean实例的全限定名作为beanNamepublic static void main(String[] args) { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); UserDao bean = (UserDao) applicationContext.getBean("org.example.UserDaoImpl"); System.out.println(bean); }如果配置了id，便不能在使用Bean实例的全限定名进行获取，例如：applicationContext.getBean("org.example.UserDaoImpl");配置别名，配置别名后可以使用别名获得Bean对象实例<bean id="userDao" name="aaa,bbb" class="org.example.UserDaoImpl"></bean>2.SpringBean的配置详解1.Bean的范围配置默认情况下，单纯的Spring环境Bean的作用范围有两个：Singleton和Prototypesingleton：单例，默认值，Spring容器创建的时候，就会进行Bean的实例化，并且存储到容器内部的单例池中，每次getBean时都是从单例池中获取相同的Bean实例<bean id="userDao" class="org.example.UserDaoImpl" scope="singleton"></bean>prototype：原型，Spring容器初始化时不会创建Bean实例，只有调用getBean时才会实例化Bean，每次getBean都会创建一个新的Bean实例<bean id="userDao" class="org.example.UserDaoImpl" scope="prototype"></bean>如果是spring-webmvc的情况下，还会增加两个作用范围：request和sessionmaven导包<dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>5.3.7</version> </dependency>request：将创建的对象放在request域当做<bean id="userDao" class="org.example.UserDaoImpl" scope="request"></bean>session：将创建的对象放在session域当做<bean id="userDao" class="org.example.UserDaoImpl" scope="session"></bean>2.Bean的延迟加载当lazy-init设置为true时为延迟加载，也就是当Spring容器创建的时候，不会立即创建Bean实例，等待用到时在创建Bean实例并且存储到单例池中去，后续在使用该Bean直接冲单例池获取，本质上该Bean还是单例的，只对scope设置为singleton的Bean起作用，对prototype无效，对BeanFactory作为容器也无效<bean id="userDao" class="org.example.UserDaoImpl" lazy-init="true"></bean>3.Bean的初始化方法和销毁方法init-method：初始化时运行方法destroy-method：销毁时运行方法，单例模式容器必须显示关闭才会执行这个方法，否则不会执行关闭，又因为ApplicationContext的接口没有关闭容器的方法，所以类型需要使用ClassPathXmlApplicationContext，才有close显式关闭容器，如果不使用显式关闭，则有可能不会执行销毁方法，例如容器挂掉后就无法执行销毁方法beans.xml:<bean id="userDao" class="org.example.UserDaoImpl" init-method="init" destroy-method="destroy"></bean>UserDaoImpl.javapublic class UserDaoImpl implements UserDao{ public void init(){ System.out.println("初始化方法"); } public void destroy(){ System.out.println("销毁方法"); } }主函数调用 public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); UserDao userDao = (UserDao) applicationContext.getBean("userDao"); System.out.println(userDao); applicationContext.close(); }结果输出初始化方法 org.example.UserDaoImpl@7d68ef40 销毁方法扩展：除此之外，我们还可以通过实现InitializingBean接口，完成一些Bean的初始化操作，比init-method方法优先级要高UserDaoImpl.javapublic class UserDaoImpl implements UserDao, InitializingBean { public void init(){ System.out.println("初始化方法"); } public void destroy(){ System.out.println("销毁方法"); } @Override public void afterPropertiesSet() throws Exception { System.out.println("属性执行之后进行调用"); } }主函数调用public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); UserDao userDao = (UserDao) applicationContext.getBean("userDao"); System.out.println(userDao); applicationContext.close(); }结果输出属性执行之后进行调用 初始化方法 org.example.UserDaoImpl@5b0abc94 销毁方法4.Bean的实例化配置Spring的实例化方式主要如下两种：构造方式实例化：底层通过构造方法对Bean进行实例化工厂方式实例化：底层通过调用自定义的工厂方法对Bean进行实例化构造方式实例化Bean分为有参构造和无参构造方法实例化，Spring中配置的<bean>几乎都是无参构造，有参构造例子如下：UserDaoImpl.javapublic class UserDaoImpl implements UserDao { public UserDaoImpl(String name){ System.out.println(name); } }有参构造在实例化Bean时，需要参数的注入，通过constructor-arg标签，嵌入在bean标签内部提供构造参数beans.xml<bean id="userDao" class="org.example.UserDaoImpl"> <constructor-arg value="你好"/> </bean>工厂方式实例化Bean，又分为如下三种：静态工厂方法实例化Bean实例工厂方法实例化Bean实现FactoryBean规范延迟实例化Bean静态工厂实例化Bean：创建一个静态方法public class MyBeanFactory1 { public static UserDao userDao(){ return new UserDaoImpl(); } }配置beans.xml文件，factory-method指定静态方法，如果有传参也需要constructor-arg进行传值<bean id="userDao1" class="factory.MyBeanFactory1" factory-method="userDao"></bean>主函数调用public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); Object useDao1 = applicationContext.getBean("userDao1"); System.out.println(useDao1); }执行结果org.example.UserDaoImpl@159f197实例工厂方法化Bean：创建一个方法public class MyBeanFactory2 { public UserDao userDao(){ return new UserDaoImpl(); } }beans.xml中配置该静态方法对bean，并且再次配置一个bean指向该bean，并且使用方法，如果有传参也需要constructor-arg进行传值<!-- 配置工厂对象 --> <bean id="myBeanFactory2" class="factory.MyBeanFactory2"></bean> <bean id="userDao2" factory-bean="myBeanFactory2" factory-method="userDao"></bean>主函数执行 public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); Object userDao2 = applicationContext.getBean("userDao2"); System.out.println(userDao2); }结果输出org.example.UserDaoImpl@51e5fc98实现FactoryBean规范延迟实例化Bean类的接口继承于FactoryBean，在BeanFactory创建时便已经创建实例，但是实例的值并不是真实的对象本身，而是当getBean进行调用的时候，才会将实例对象新建调用getObject方法并且存放到缓存池，然后从缓存池取值从而返回实例对象，如果后续进行重复取值，不会再创建一个新的对象，而是从缓存池取值后直接返回，从而实现FactoryBean规范延迟加载Beanpublic class MyBeanFactory3 implements FactoryBean<UserDao> { @Override public UserDao getObject() throws Exception { return new UserDaoImpl(); } @Override public Class<?> getObjectType() { return null; } }主函数调用public static void main(String[] args) { ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); Object userDao3 = applicationContext.getBean("userDao3"); Object userDao4 = applicationContext.getBean("userDao3"); System.out.println(userDao3); System.out.println(userDao4); }运行结果org.example.UserDaoImpl@48fa0f47 org.example.UserDaoImpl@48fa0f475.Bean的注入方式 其中，ref是reference的缩写，翻译为参考涉及到意思，用于引入其他Bean的id。value用于注入普通的属性值。6.Bean的依赖注入配置配置注入普通类型的List对象配置接口public interface UserService { public List<String> getStringList(); }配置实现类public class UserServiceImpl implements UserService { //注入List private List<String> stringList; public void setStringList(List<String> stringList) { this.stringList = stringList; } public List<String> getStringList() { return stringList; } }配置Beans.xml文件<bean id="userService" class="org.example.UserServiceImpl"> <property name="stringList"> <list> <value>aaaa</value> <value>bbbb</value> <value>cccc</value> <value>dddd</value> </list> </property> </bean>主函数运行ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); UserService userService = (UserService) applicationContext.getBean("userService"); System.out.println(userService.getStringList());运行结果[aaaa, bbbb, cccc, dddd]配置注入引用类型的List对象UserServicelmpl.javapublic List<String> getStringList() { return stringList; } public void setUserDaoList(List<UserDao> userDaoList) { this.userDaoList = userDaoList; }beans.xml需要配置ref或者单独创建bean<bean id="useService1" class="org.example.UserServiceImpl"> <property name="userDaoList"> <list> <bean class="org.example.UserDaoImpl"/> <bean class="org.example.UserDaoImpl"/> <bean class="org.example.UserDaoImpl"/> <bean class="org.example.UserDaoImpl"/> </list> </property> </bean>或者<bean id="userDao1" class="org.example.UserDaoImpl"/> <bean id="userDao2" class="org.example.UserDaoImpl"/> <bean id="userDao3" class="org.example.UserDaoImpl"/> <bean id="userDao4" class="org.example.UserDaoImpl"/> <bean id="useService1" class="org.example.UserServiceImpl"> <property name="userDaoList"> <list> <ref bean="userDao1"/> <ref bean="userDao2"/> <ref bean="userDao3"/> <ref bean="userDao4"/> </list> </property> </bean>配置注入引用类型的set对象配置和List一样，在beans.xml文件中，将list标签改为set配置注入引用类型的map对象配置和List一样，在beans.xml文件中，将list标签改为map，map中标签为entry，key为键名，value为键值，value-ref为引用对象<property name="map"> <map> <entry key="a" value="1111"/> <entry key="b" value="2222"/> </map> </property> <property name="map"> <map> <entry key="a" value-ref="userDao1"/> <entry key="b" value-ref="userDao2"/> </map> </property>

Java BeanFactory与ApplicationContext的关系与继承体系 BeanFactory与ApplicationContext的关系BeanFactory是Spring的早期接口，成为Spring的Bean工厂，ApplicationContext是后期更高级接口，称之为Spring容器；ApplicationContext在BeanFactory基础上对功能进行了扩展，例如：监听功能、国际化功能等。BeanFactory的API更偏向于底层，ApplicationContext的API大多数是对这些底层API的封装Bean创建的主要逻辑和功能都被封装在BeanFactory中，ApplicationContext不仅继承了BeanFactory，而且ApplicationContext内部还维护着BeanFactory的引用，所以ApplicationContext与BeanFactory既有继承关系，又有融合关系Bean的初始化时机不同，原始BeanFactory是在首次调用getBean时才进行Bean的创建，而ApplicationContext则是配置文件加载，容器一创建就将Bean都实例化初始化好BeanFactorypublic static void main(String[] args) { // 创建工厂对象 DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory(); // 创建一个读取器（xml文件） XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(beanFactory); // 读取配置文件给工厂 reader.loadBeanDefinitions("beans.xml"); // 根据id获取bean实例对象，Bean在此时创建对象 UserService userService = (UserService) beanFactory.getBean("userService"); System.out.println(userService); }ApplicationContextpublic static void main(String[] args) { // 读取配置文件的时候便已经实例化初始化完成 ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); UserService userService = (UserService) applicationContext.getBean("userService"); System.out.println(userService); }BeanFactory与ApplicationContext的继承体系BeanFactor的继承体系BeanFactory是核心接口，项目运行过程中肯定有具体实现参与，这个具体实现就是DefaultListtableBeanFactory，而ApplicationContext内部维护的BeanFactory的实现类也是它ApplicationContext的继承体系只在Spring基础环境下，即只导入spring-context坐标时，此时ApplicationContext的继承体系 只在Spring基础环境下，常用的三个ApplicationContext作用如下：

Java ApplicationContext Java ApplicationContext快速入门ApplicationContext成为Spring容器，内部封装了BeanFactory，笔BeanFactory功能更丰富更强大，使用ApplicationContext进行开发式，xml配置文件的名称习惯写成applicationContent.xml1.使用ApplicationContext调用BeanFactory基础配置可看上一篇文章 点我跳转public static void main(String[] args) { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml"); UserService userService = (UserService) applicationContext.getBean("userService"); System.out.println(userService); }运行结果：BeanFactory去调用该方法 从容器中获得userDao设置到此处org.example.UserDaoImpl@1e730495 org.example.UserServiceImpl@318ba8c8

Java BeanFactory Java BeanFactory快速入门Ioc思想实现1.创建普通的Maven项目2.在pom.xml文件中的project标签内导入Spring的jar包<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> ...... <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>5.3.7</version> </dependency> </dependencies> </project>3.创建UserService接口4.创建UserServiceImpl类，并且继承UserService接口5.在resources中创建beans.xml文件，并且配置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 id="userService" class="org.example.UserServiceImpl"></bean> </beans>6.主函数运行 public static void main(String[] args) { // 创建工厂对象 DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory(); // 创建一个读取器（xml文件） XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(beanFactory); // 读取配置文件给工厂 reader.loadBeanDefinitions("beans.xml"); // 根据id获取bean实例对象 UserService userService = (UserService) beanFactory.getBean("userService"); System.out.println(userService); }DI思想实现，依赖注入1.创建UserDao接口和UserDaoIpml类，类继承UserDao接口2.在UserServiceImpl类中新建一个set方法，用于接受设置注入的对象 public class UserServiceImpl implements UserService{ // BeanFactory去调用该方法 从容器中获得userDao设置到此处 public void setUserDao(UserDao userDao){ System.out.println("BeanFactory去调用该方法 从容器中获得userDao设置到此处" + userDao); } }3.配置beans.xml文件，在bean标签中添加property标签实现依赖注入 <?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="userService" class="org.example.UserServiceImpl"> <property name="userDao" ref="userDao"></property> </bean> <bean id="userDao" class="org.example.UserDaoImpl"></bean> </beans>4.主函数调用，完成依赖注入 // 创建工厂对象 DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory(); // 创建一个读取器（xml文件） XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(beanFactory); // 读取配置文件给工厂 reader.loadBeanDefinitions("beans.xml"); // 根据id获取bean实例对象 UserService userService = (UserService) beanFactory.getBean("userService"); System.out.println(userService);BeanFactory去调用该方法 从容器中获得userDao设置到此处org.example.UserDaoImpl@49c43f4e org.example.UserServiceImpl@290dbf45