Spring基于注解的IoC和DI

配置自动扫描的包

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd">
    <context:component-scan base-package="com.ttpfx"/>
</beans>

Bean注解

• @Component(["beanId"])
• @Controller(["beanId"]) 用于表现层
• @Service(["beanId"]) 用于业务层
• @Repository(["beanId"]) 用于持久层

若不指定，则Bean的id为首字母小写的类名：accountServiceImpl

@Component("accountService")
public class AccountServiceImpl implements AccountService {
    // ... 
}

等价于：

<bean id="accountService" class="com.ttpfx.service.AccountServiceImpl"/>

Bean的作用域

• @Scope

@Component("accountService")
@Scope("singleton")
public class AccountServiceImpl implements AccountService {
    // ... 
}

等价于：

<bean id="accountService" class="com.ttpfx.service.AccountServiceImpl" scope="singleton"/>

生命周期

• @PostConstruct 用于注解初始化方法，相当于bean标签的init-method属性
• @PreDestroy 用于注解销毁方法，相当于bean标签的destroy-method属性

@Component("accountService")
public class AccountServiceImpl implements AccountService {
    @PostConstruct
    private void init() {
        System.out.println("AccountServiceImpl.init() 执行");
    }

    @PreDestroy
    private void destroy() {
        System.out.println("AccountServiceImpl.destroy() 执行");
    }
}

等价于：

<bean id="accountService" class="com.ttpfx.service.AccountServiceImpl" init-method="init" destroy-method="destroy"/>

注入

• @Autowired: 首先根据类型匹配，若该类型的bean不唯一，再根据变量名进行匹配
• @Qualifier("beanId")：注解成员属性时，不能单独使用，需要与@Autowired配合使用；根据beanId匹配
• @Resource(name="beanId")：可单独使用，根据beanId匹配
• @Value("value"):注入基本类型或String

@Component("accountService")
public class AccountServiceImpl implements AccountService {
    @Autowired
    @Qualifier("accountDao2")
    private AccountDao accountDao;
}

@Component("accountService")
public class AccountServiceImpl implements AccountService {
    @Resource(name = "accountDao2")
    private AccountDao accountDao;
}

@Component("account")
public class Account {
    @Value("1")
    private Integer id;
    @Value("ZhangSan")
    private String username;
}

配置类

• @Configuration 注解当前类为配置类
• @ComponentScan("package") 注解自动扫描的包
• @ComponentScans([@ComponentScan])
• @Bean([name = "beanId"]) 注解方法的返回值为Bean类
• @Import（Config.class) 导入配置类
• @PropertySource("classpath:path") 导入properties配置文件，"classpath："表示从类路径下加载配置文件

@Configuration
@Import({JdbcConfig.class})
@ComponentScans({@ComponentScan("com.ttpfx")})
public class SpringConfig {
}

@Configuration
@PropertySource("classpath:jdbc.properties")
public class JdbcConfig {
    @Value("${jdbc.driver}")
    private String jdbcDriver;

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

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

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

    @Bean(name = "queryRunner")
    @Scope("prototype")
    public QueryRunner createQueryRunner(DataSource dataSource) {
        return new QueryRunner(dataSource);
    }

    @Bean(name = "dataSource")
    public DataSource createDataSource() {
        try {
            ComboPooledDataSource dataSource = new ComboPooledDataSource();
            dataSource.setDriverClass(jdbcDriver);
            dataSource.setJdbcUrl(jdbcUrl);
            dataSource.setUser(jdbcUsername);
            dataSource.setPassword(jdbcPassword);
            return dataSource;
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

等价于：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd">
    <context:component-scan base-package="com.ttpfx"/>
  
    <bean id="queryRunner" class="org.apache.commons.dbutils.QueryRunner">
        <constructor-arg name="ds" ref="dataSource"/>
    </bean>

    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="com.mysql.cj.jdbc.Driver"/>
        <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/t_mybatis"/>
        <property name="user" value="root"/>
        <property name="password" value="123456"/>
    </bean>
</beans>