Spring

IOC理论

1.场景：
	传统开发：三层架构之间要组合调用，通过new调用对象实现
	userDao 接口
	UserDaoimpl 实现类
	
	UserService 业务接口
	UserSerciveImpl 业务实现类
	
	问题：service组合时UserDao userdao = new MysqlImp()
									new OrcaleImp()//多态所引起的，会需要调用处写死多个实现类对象，用户的不同需求会影响原来的代码
	解决：
		1.用set实现动态注入需要的实现类对象，以便调后续的方法，将主动new对象权释放

spring的本质是ioc,控制反转：即我们主动new对象这一过程被第三方给接管，由第三方实现。

配置步骤

1.引入maven依赖
2.编写配置文件（官网有）

	
    
    
      
            	
            
    

    
        
    

    


每一个bean标签接管一个对象的创建，其中id是唯一标识通过它来get容器中的对象，class是标识对象的全限定类名
property:对象中要注入的属性 ref使用容器中创建好的对象
import：引入其他的配置文件（mybatis.xml）

3使用：
ApplicationContext context = new ClassPathXmlApplicationContext("配置文件名.xml");
PetStoreService service = context.getBean("petStore", PetStoreService.class);

基于XML

1.默认走的无参构造

2.使用构造器有参构造注入

Constructor Argument Resolution：
    
	方式一：
    public class ThingOne {

    public ThingOne(ThingTwo thingTwo, ThingThree thingThree) {
        // ...
    }
}
    
        
        
    
    方式二：type matching
public class ExampleBean {

    // Number of years to calculate the Ultimate Answer
    private final int years;

    // The Answer to Life, the Universe, and Everything
    private final String ultimateAnswer;

    public ExampleBean(int years, String ultimateAnswer) {
        this.years = years;
        this.ultimateAnswer = ultimateAnswer;
    }
}

    
    

    
    方式三：index参数下标

    
    

    方式四：通过名称

    
    

3.复杂类型注入

bean | ref | idref | list | set | map | props | value | null

4.c p 命名空间

相当于语法糖：省略property和constructor
	 xmlns:p="http://www.springframework.org/schema/p"
	 
		xmlns:c="http://www.springframework.org/schema/c"
		

5.bean的作用域可以设置

6.隐式自动装配

with the autowire attribute of the  element.加上 autowire属性

基于注解

1.开启注解和扫描包(加上value不然出bug)
2在类上	  @Conponent 
        @Repository
        @Service
        @control 类即被spring接管id默认为首字母小写

• @Required:应用于set方法

The @Required annotation applies to bean property setter methods, as in the following example:
public class SimpleMovieLister {

    private MovieFinder movieFinder;

    @Required
    public void setMovieFinder(MovieFinder movieFinder) {
        this.movieFinder = movieFinder;
    }

    // ...
}

• @Autowired：应用于set函数和属性上

You can apply the @Autowired annotation to constructors, as the following example shows:
public class MovieRecommender {

    private final CustomerPreferenceDao customerPreferenceDao;

    @Autowired
    public MovieRecommender(CustomerPreferenceDao customerPreferenceDao) {
        this.customerPreferenceDao = customerPreferenceDao;
    }

    // ...
}
前提要注入的bean在ioc中已经存在默认通过name装配

• @Primary：优先默认装配

@Configuration
public class MovieConfiguration {

    @Bean
    @Primary
    public MovieCatalog firstMovieCatalog() { ... }

    @Bean
    public MovieCatalog secondMovieCatalog() { ... }

    // ...
}

public class MovieRecommender {

    @Autowired
    private MovieCatalog movieCatalog;

    // ...
}
优先装配到加了@Primary

• @Qualifier:配合 @Autowired指定xml中的哪一个bean装配给谁最好指定value

public class MovieRecommender {

    @Autowired
    @Qualifier("main")
    private MovieCatalog movieCatalog;

    // ...
}
public class MovieRecommender {

    private MovieCatalog movieCatalog;

    private CustomerPreferenceDao customerPreferenceDao;

    @Autowired
    public void prepare(@Qualifier("main") MovieCatalog movieCatalog,
            CustomerPreferenceDao customerPreferenceDao) {
        this.movieCatalog = movieCatalog;
        this.customerPreferenceDao = customerPreferenceDao;
    }

    // ...
}

• @Resource(name=“xx”)
• @vlaue注入属性值

基于注解的配置

@Configuration
public class AppConfig {

    @Bean
    public MyService myService() {
        return new MyServiceImpl();
    }
}

等价于

• 使用

public static void main(String[] args) {
    ApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfig.class);
    MyService myService = ctx.getBean(MyService.class);
    myService.doStuff();
}

开启包扫描

@Configuration
@ComponentScan(basePackages = "com.acme") 
public class AppConfig  {
    // ...
}

注册其他的配置文件

public static void main(String[] args) {
    AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
    ctx.register(AppConfig.class, OtherConfig.class);
    ctx.register(AdditionalConfig.class);
    ctx.refresh();
    MyService myService = ctx.getBean(MyService.class);
    myService.doStuff();
}

@Bean(“name”)在方法上方法名即为id名

@Configuration
public class AppConfig {

    @Bean
    public TransferServiceImpl transferService() {
        return new TransferServiceImpl();
    }
}

等价于

使用@Import(ConfigA.class)

@Configuration
public class ConfigA {

    @Bean
    public A a() {
        return new A();
    }
}
@Configuration
@Import(ConfigA.class)
public class ConfigB {

    @Bean
    public B b() {
        return new B();
    }
}

配置类引入xml

@Configuration
@ImportResource("classpath:/com/acme/properties-config.xml")
public class AppConfig {

    @Value("${jdbc.url}")
    private String url;

    @Value("${jdbc.username}")
    private String username;

    @Value("${jdbc.password}")
    private String password;

    @Bean
    public DataSource dataSource() {
        return new DriverManagerDataSource(url, username, password);
    }
}