Spring5（6）- 新注解 Configuration 和 ComponentScan，Bean

1 配置类

package com.tzb.config;

import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.apache.commons.dbutils.QueryRunner;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Scope;

import javax.sql.DataSource;

/**
 * 配置类,作用和 bean.xml 一样
 * 

 * 新注解：
 * (1)Configuration,指定当前类是一个配置类
 * 

 * （2）ComponentScan ，通过注解指定spring在创建容器时扫描的包
 * 属性
 * value:它和 basePackages的作用是一样的
 * 

 * (3)Bean
 * 用于把当前方法的返回值作为 bean 对象存入 spring ioc容器
 * 属性：
 * name : 用于指定bean 的id。默认值是当前方法的名称
 *
 * --------------------------
 * 细节：当使用注解配置方法时，如果方法有参数，spring会去容器中查找有没有可用的 bean 对象，
 *    查找的方式和 Autowired 注解的作用一样
 *
 */
@Configuration
@ComponentScan(basePackages = "com.tzb")
public class SpringConfiguration {

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

    @Bean(name = "dataSource")
    public DataSource createDateSource() {
        ComboPooledDataSource ds = new ComboPooledDataSource();
        try {
            ds.setDriverClass("com.mysql.jdbc.Driver");
            ds.setJdbcUrl("jdbc:mysql://localhost:3306/spring5?userSSL=false");
            ds.setUser("root");
            ds.setPassword("root");
            return ds;
        }catch (Exception e){
            throw new RuntimeException(e);
        }
    }
}

1.1 @import

• 用于导入其他的配置类
• 属性：value : 指定其他类的字节码
• 有 import 注解的就是父配置类，导入的都是子配置类

---

• 子配置类

package com.tzb.config;

import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.apache.commons.dbutils.QueryRunner;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Scope;

import javax.sql.DataSource;

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

    @Bean(name = "dataSource")
    public DataSource createDateSource() {
        ComboPooledDataSource ds = new ComboPooledDataSource();
        try {
            ds.setDriverClass("com.mysql.jdbc.Driver");
            ds.setJdbcUrl("jdbc:mysql://localhost:3306/spring5?userSSL=false");
            ds.setUser("root");
            ds.setPassword("root");
            return ds;
        }catch (Exception e){
            throw new RuntimeException(e);
        }
    }
}

• 父配置类

@ComponentScan(basePackages = "com.tzb")
@Import(value = JdbcConfig.class)
public class SpringConfiguration {


}

2 AnnotationConfigApplicationContext

• 单元测试

    @Test
    public void testFindOne(){
        // 获取容器
        //ApplicationContext ac = new ClassPathXmlApplicationContext("bean.xml");
        ApplicationContext ac = new AnnotationConfigApplicationContext(SpringConfiguration.class);

        IAccountService as = ac.getBean("accountService", AccountServiceImpl.class);

        Account account = as.findAccountById(1);
        System.out.println(account);
    }

---

3 注解 PropertySource

指定 properties 文件的位置

---

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/spring5?userSSL=false
jdbc.username=root
jdbc.password=root

---

• 子配置类

public class JdbcConfig {

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

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

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

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

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

    @Bean(name = "dataSource")
    public DataSource createDateSource() {
        ComboPooledDataSource ds = new ComboPooledDataSource();
        try {
            ds.setDriverClass(driver);
            ds.setJdbcUrl(url);
            ds.setUser(username);
            ds.setPassword(password);
            return ds;
        }catch (Exception e){
            throw new RuntimeException(e);
        }
    }
}

• 父配置类

@ComponentScan(basePackages = "com.tzb")
@Import(value = JdbcConfig.class)
@PropertySource("classpath:jdbc.properties")
public class SpringConfiguration {


}

4 Qualifier注解的另一种用法

• 一个对象有多个实现类的情况