四.简化Spring XML的配置

向右看齐 2022-06-17 13:39 242阅读 0赞

**一.自动装配**  
byName:

byType:

constructor:

autodetect:

可以在属性中加default-autowire=“byType”开启

此外自动和手动和混合：

**二.基于注解的配置.**  
定义Bean的注解：  
@Component  
@Controller  
@Repository  
@Service

标注后扫描类包加载定义的Bean

xmlns:context="http://www.springframework.org/schema/context"    ① 
      <context:component-scan   base-package="com.jike.spring"/>   ②

**生命周期注解：**  
以前：

现在：

public class PersonService {   
        @PostConstruct  
        public void  init(){  ……}  
        @PreDestroy  
        public void  dostory(){  …… }  
    } 
    <context:annotation-config />

**常用注解详解：**

@Service①
    public class LogonService { 
        @Autowired②
        private LogDao logDao;
    }
    
    public class LogonService { 
        @Autowired（required=false）③
        private LogDao logDao;
    }
    
    public class LogonService { 
        @Autowired
        @Qualifier(“userDao”)④
        private UserDao userDao;
    }

@Autowired标注方法入参示例：

public class LogonService { 
        @Autowired①
         public void setLogDao(LogDao logDao) {
                  this.logDao = logDao;
          }
         @Autowired
         @Qualifier(“userDao”) ②
         public void setUserDao(UserDao userDao) {
                  this.userDao = userDao;
          }
    }
    
    @Autowired
    public void init(@Qualifier(“userDao”)UserDao userDao) {③
        this.userDao = userDao;
    }

@Autowired标注集合入参示例：

public class LogonService {
        @Autowired(required=false) ①
        public List<Plugin> plugins ;
        public List<Plugin> getPlugins() {
            return plugins;
        }
    }

**三.基于JAVA类的配置：目的消灭XML**  
JAVA类定义Bean配置元数据步骤：  
@Configuration注解需要作为配置的类  
@Bean注解相应的方法  
AnnotationConfigApplicationContext或子类进行加载

@Configuration   
    public class ApplicationContextConfig {  
        @Bean  
        public String message() {  
            return "hello";  
        }  
    } 
    
    加载：
    public class ConfigurationTest {
        public static void main(String[] args) {
            AnnotationConfigApplicationContext ctx =
            new AnnotationConfigApplicationContext(ApplicationContextConfig.class);
            System.out.println(ctx.getBean("message"));
        }
    }

@Bean

@Bean
    public String message() {
        return new String("hello");
    }
    <bean id="message" class="java.lang.String">  
        <constructor-arg index="0" value="hello"/>  
    </bean>