Bean的Scope

每一個bean可以新增Scope標籤來設定

個人理解從此看出Spring的控制反轉預設一直都在用一個例項注入

1.Singleton 一個Spring容器中只有一個Bean的例項，此為Spring的預設配置，全容器共享一個例項。

2.Prototype 每次呼叫一個新建一個Bean的例項

3.Request Web專案中，給每一個http request 新建一個Bean例項。

4.Session Web專案中，給每一個http session新建一個Bean例項。

5.GlobalSession 這個只在portal應用中有用，給每一個global http session 新建一個例項。

可以拿小例子是演示一下預設的singleton 和 Prototype的結果

建立一個空的service，一個標註上@Scope("prototye") ，一個預設

@Service
@Scope("prototype")
public class DemoPrototypeService {

}

@Service
public class DemoSingletonService {

}

在config類加入掃描包註解

@Configuration
@ComponentScan("com.cn.sola.service")
public class SpringConfig {

}

然後用反射在測試類測試看結果

@RunWith(SpringRunner.class)
@SpringBootTest
public class SpringBootShiZhanApplicationTests {

	@Test
	public void contextLoads() {
		
	AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
	
	DemoSingletonService d1 = context.getBean(DemoSingletonService.class);
	DemoSingletonService d2 = context.getBean(DemoSingletonService.class);
	
	System.out.println(d1.equals(d2));
	
	DemoPrototypeService p1 = context.getBean(DemoPrototypeService.class);
	DemoPrototypeService p2 = context.getBean(DemoPrototypeService.class);
	
	System.out.println(p1.equals(p2));
	}

}
 

結果就是DemoSingletonService結果為True，DemoPrototypeService為False。

由此看出Spring加Bean註解的都是一個例項。

Spring EL和資源的呼叫

未來的大牛

簡單來說就是例如註解直接注入變數的值

首先為了方便先加入一個io工具依賴

		<!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
		<dependency>
			<groupId>commons-io</groupId>
			<artifactId>commons-io</artifactId>
			<version>2.6</version>
		</dependency>

然後可以在com.cn.sola包下建立一個test.properties,一個test.txt

比如test.properties裡可以寫

book.author=solatest
book.name=spring boot

txt可以寫

未來的大牛

需要注入的bean（其中一個service）

package com.cn.sola.service;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;

@Service
public class DemoService {
	@Value("其他類的屬性")
	private String another;

	public String getAnother() {
		return another;
	}

	public void setAnother(String another) {
		this.another = another;
	}

}

另一個service

package com.cn.sola.service;

import org.apache.commons.io.IOUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
import org.springframework.core.env.Environment;
import org.springframework.core.io.Resource;
import org.springframework.stereotype.Service;

@Service
public class SpringService {
	//直接注入字串
	@Value("I Love You!")
	private String normal;
	
	//注入當前系統的操作環境(當前結果window10)
	@Value("#{systemProperties['os.name']}")
	private String osName;
	
	//注入一個隨機數
	@Value("#{T(java.lang.Math).random()*100.0}")
	private double randomNumber;
    
	//注入demoService下String型別another引數的值
	@Value("#{demoService.another}")
	private String fromAnother;
	
	//注入了一個檔案型別
	@Value("classpath:com/cn/sola/bean/test.txt")
	private Resource testFile;
	
	//暫時不明
	@Value("http://www.baidu.com")
	private Resource testUrl;
	
	//注入了test.properties下book.name的值
	@Value("${book.name}")
	private String bookName;
	
	//這類應該是可以直接獲取properties的鍵值對
	@Autowired
	private Environment environment;
	
	//不明
	@Bean
	public static PropertySourcesPlaceholderConfigurer propertyConfigure(){
		return new PropertySourcesPlaceholderConfigurer();
	}
	
	public void outputResource(){
		try{
			
			System.out.println(normal);
			System.out.println(osName);
			System.out.println(randomNumber);
			System.out.println(fromAnother);
			
			//commons-io依賴的方法
			System.out.println(IOUtils.toString(testFile.getInputStream()));
			System.out.println(IOUtils.toString(testUrl.getInputStream()));
			System.out.println(bookName);
			//用這個方法可以用key值獲取到value，但是也要宣告properties的位置@PropertySource("classpath:com/cn/sola/bean/test.properties")
			System.out.println(environment.getProperty("book.author"));
		}catch(Exception e){
			
			e.printStackTrace();
		}
	}
	
	
}

配置類

package com.cn.sola.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

@Configuration
@ComponentScan("com.cn.sola.service")
@PropertySource("classpath:com/cn/sola/bean/test.properties")
public class ResourceConfig {

}

測試類

package com.cn.sola;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.test.context.junit4.SpringRunner;

import com.cn.sola.config.ResourceConfig;
import com.cn.sola.service.SpringService;

@RunWith(SpringRunner.class)
@SpringBootTest
public class SpringBootShiZhanApplicationTests {

	@Test
	public void contextLoads() {
		
	   AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ResourceConfig.class);
	
	   SpringService service = context.getBean(SpringService.class);
	   
	   service.outputResource();
	   
	   context.close();
	}

}

輸出結果就和想象的一樣啦------------

Bean的初始化和銷燬

首先新增一個依賴，原文中用的JSR-250，現在只用這個就可以

		<!-- https://mvnrepository.com/artifact/javax.annotation/javax.annotation-api -->
		<dependency>
			<groupId>javax.annotation</groupId>
			<artifactId>javax.annotation-api</artifactId>
			<version>1.3.2</version>
		</dependency>

我們實際開發的時候，經常會遇到在Bean在使用之前或者之後做些必要的操作，Spring對Bean的生命週期的操作提供了支援

有兩種方式

（1）Java配置方式：使用@Bean的initMethod 和 destroyMethod例子 //這個在配置類裡寫

  (2)  註解方式：需要新增依賴利用JSR-250的@PostConstruct和@PreDestroy    //JSR-250現在已經包含在

使用@Bean形式的Bean   得在配置類裡宣告

package com.cn.sola.service;

public class BeanWayService {

	public void init(){
		
		System.out.println("@Bean-init-method");
	}
	public BeanWayService(){
		super();
		System.out.println("初始化建構函式-BeanWayService");
	}
	public void destroy(){
		
		System.out.println("@Bean-destroy-method");
	}
}

使用JSR250形式的Bean  在類裡就可宣告

package com.cn.sola.service;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

public class JSR250WayService {
	
	@PostConstruct
	public void init(){
		System.out.println("jsr250-init-method");
	}
	public JSR250WayService(){
		super();
		System.out.println("初始化構造引數-JSR250WayService");
	}
	@PreDestroy
	public void destroy(){
		System.out.println("jsr250-destory-method");
	}

}

配置類     @Bean配置在此配置初始和銷燬方法

package com.cn.sola.config;

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

import com.cn.sola.service.BeanWayService;
import com.cn.sola.service.JSR250WayService;

@Configuration
@ComponentScan("com.cn.sola.service")
public class ResourceConfig {

	@Bean(initMethod="init",destroyMethod="destroy")//這裡可以設定初始的呼叫方法
	BeanWayService beanWayService(){
		return new BeanWayService();
	}
	@Bean
	JSR250WayService jsr250WayService(){
		return new JSR250WayService();
	}
	
}

下面是小測試類

package com.cn.sola;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.test.context.junit4.SpringRunner;

import com.cn.sola.config.ResourceConfig;
import com.cn.sola.service.BeanWayService;
import com.cn.sola.service.JSR250WayService;

@RunWith(SpringRunner.class)
@SpringBootTest
public class SpringBootShiZhanApplicationTests {

	@Test
	public void contextLoads() {
		
	   AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ResourceConfig.class);
	
	   context.getBean(BeanWayService.class);
	   
	   context.getBean(JSR250WayService.class);
	   
	   context.close();
	}

}

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.0.3.RELEASE)

2018-07-05 19:41:12.182  INFO 9204 --- [           main] c.c.s.SpringBootShiZhanApplicationTests  : Starting SpringBootShiZhanApplicationTests on DESKTOP-LN7MO04 with PID 9204 (started by JAVA in D:\SpringBootWorkSpace\SpringBootShiZhan)
2018-07-05 19:41:12.184  INFO 9204 --- [           main] c.c.s.SpringBootShiZhanApplicationTests  : No active profile set, falling back to default profiles: default
初始化建構函式-BeanWayService
@Bean-init-method
初始化構造引數-JSR250WayService
jsr250-init-method
2018-07-05 19:41:14.125  INFO 9204 --- [           main] c.c.s.SpringBootShiZhanApplicationTests  : Started SpringBootShiZhanApplicationTests in 2.285 seconds (JVM running for 3.023)
2018-07-05 19:41:14.240  INFO 9204 --- [           main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.spring[email protected]5c20ffa8: startup date [Thu Jul 05 19:41:14 CST 2018]; root of context hierarchy
初始化建構函式-BeanWayService
@Bean-init-method
初始化構造引數-JSR250WayService
jsr250-init-method
2018-07-05 19:41:14.278  INFO 9204 --- [           main] s.c.a.AnnotationConfigApplicationContext : Closing org.spring[email protected]5c20ffa8: startup date [Thu Jul 05 19:41:14 CST 2018]; root of context hierarchy
jsr250-destory-method
@Bean-destroy-method
jsr250-destory-method
@Bean-destroy-method