spring5教程（二）——core

短命女 2022-05-27 01:55 147阅读 0赞

## ioc容器和beans ##

> IOC也叫DI，org.springframework.beans and org.springframework.context 是ioc容器的基础包。BeanFactory接口提供基础功能，ApplicationContext 是BeanFactory的扩展。

## 代码 ##

services.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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    
        
    
        <bean id="petStore" class="org.springframework.samples.jpetstore.services.PetStoreServiceImpl">
            <property name="accountDao" ref="accountDao"/>
            <property name="itemDao" ref="itemDao"/>
            
        </bean>
    
        
    
    </beans>

daos.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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    
        <bean id="accountDao" class="org.springframework.samples.jpetstore.dao.jpa.JpaAccountDao">
            
        </bean>
    
        <bean id="itemDao" class="org.springframework.samples.jpetstore.dao.jpa.JpaItemDao">
            
        </bean>
    
        
    
    </beans>

// create and configure beans
    ApplicationContext context = new ClassPathXmlApplicationContext("services.xml", "daos.xml");
    
    // retrieve configured instance
    PetStoreService service = context.getBean("petStore", PetStoreService.class);
    
    // use configured instance
    List<String> userList = service.getUsernameList();

## bean配置属性 ##

**静态方法注入**

public class ClientService {
        private static ClientService clientService = new ClientService();
        private ClientService() {}
    
        public static ClientService createInstance() {
            return clientService;
        }
    }

**非静态方法注入**

<bean id="serviceLocator" class="examples.DefaultServiceLocator">
        
    </bean>
    
    
    <bean id="clientService" factory-bean="serviceLocator" factory-method="createClientServiceInstance"/>

public class DefaultServiceLocator {
    
        private static ClientService clientService = new ClientServiceImpl();
    
        public ClientService createClientServiceInstance() {
            return clientService;
        }
    }

**一个工厂多个方法**

public class DefaultServiceLocator {
    
        private static ClientService clientService = new ClientServiceImpl();
    
        private static AccountService accountService = new AccountServiceImpl();
    
        public ClientService createClientServiceInstance() {
            return clientService;
        }
    
        public AccountService createAccountServiceInstance() {
            return accountService;
        }
    }

**构造器注入**

package x.y;
    
    public class Foo {
    
        public Foo(Bar bar, Baz baz) {
            // ...
        }
    }

**构造器注入参数问题**

package examples;
    
    public class ExampleBean {
    
        // Number of years to calculate the Ultimate Answer
        private int years;
    
        // The Answer to Life, the Universe, and Everything
        private String ultimateAnswer;
    
        public ExampleBean(int years, String ultimateAnswer) {
            this.years = years;
            this.ultimateAnswer = ultimateAnswer;
        }
    }

**构造函数别名**

package examples;
    
    public class ExampleBean { 
    
        // Fields omitted
    
        @ConstructorProperties({
       "years", "ultimateAnswer"})
        public ExampleBean(int years, String ultimateAnswer) {
            this.years = years;
            this.ultimateAnswer = ultimateAnswer;
        }
    }

**Collections**

<bean id="moreComplexObject" class="example.ComplexObject">
        
        <property name="adminEmails">
            <props>
                <prop key="administrator">administrator@example.org</prop>
                <prop key="support">support@example.org</prop>
                <prop key="development">development@example.org</prop>
            </props>
        </property>
        
        <property name="someList">
            <list>
                <value>a list element followed by a reference</value>
                <ref bean="myDataSource" />
            </list>
        </property>
        
        <property name="someMap">
            <map>
                <entry key="an entry" value="just some string"/>
                <entry key ="a ref" value-ref="myDataSource"/>
            </map>
        </property>
        
        <property name="someSet">
            <set>
                <value>just some string</value>
                <ref bean="myDataSource" />
            </set>
        </property>
    </bean>

**p标签简化配置**

**c标签简化配置**

<bean id="foo" class="x.y.Foo" c:_0-ref="bar" c:_1-ref="baz"/>

**depends-on**

**Lazy-initialized**

**init-method**

<bean id="exampleInitBean" class="examples.ExampleBean" init-method="init"/>
    public class ExampleBean {
    
        public void init() {
            // do some initialization work
        }
    }

类似于

<bean id="exampleInitBean" class="examples.AnotherExampleBean"/>
    public class AnotherExampleBean implements InitializingBean { 
    
        public void afterPropertiesSet() {
            // do some initialization work
        }
    }

**destroy-method**

<bean id="exampleInitBean" class="examples.ExampleBean" destroy-method="cleanup"/>
    
    public class ExampleBean {
    
        public void cleanup() {
            // do some destruction work (like releasing pooled connections)
        }
    }

类似于

<bean id="exampleInitBean" class="examples.AnotherExampleBean"/>
    public class AnotherExampleBean implements DisposableBean { 
    
        public void destroy() {
            // do some destruction work (like releasing pooled connections)
        }
    }

**注解方式 init-method destroy-method**

public class CachingMovieLister { 
    
        @PostConstruct
        public void populateMovieCache() {
            // populates the movie cache upon initialization...
        }
    
        @PreDestroy
        public void clearMovieCache() {
            // clears the movie cache upon destruction...
        }
    }

**读取配置文件**

## Spring Bean 作用域 ##

> **singleton** 该作用域将 bean 的定义的限制在每一个 Spring IoC 容器中的一个单一实例(默认)。  
> **prototype** 该作用域将单一 bean 的定义限制在任意数量的对象实例。  
> **request** 该作用域将 bean 的定义限制为 HTTP 请求。只在 web-aware Spring ApplicationContext 的上下文中有效。  
> **session** 该作用域将 bean 的定义限制为 HTTP 会话。 只在web-aware Spring ApplicationContext的上下文中有效。  
> **global-session** 该作用域将 bean 的定义限制为全局 HTTP 会话。只在 web-aware Spring ApplicationContext 的上下文中有效。