03Spring入门

Spring IoC

Inversion of Control
控制反转
主要靠依赖注入实现
IoC容器是实现依赖注入的关键

bean调用

示例：
在test中添加注解：@ContextConfiguration(classes = CommnunityApplication.class) //启用CommunityApplication作为配置类

创建dao目录

package com.newcoder.community.dao;

public interface AlphaDao {
    public String select();
}

package com.newcoder.community.dao;

import org.springframework.stereotype.Repository;

@Repository //让容器能扫描到
public class AlphaDaoHibernateImpel implements AlphaDao{
    @Override
    public String select() {
        return "Hibernate";
    }
}

test类中

package com.newcoder.community;

import com.newcoder.community.dao.AlphaDao;
import org.junit.jupiter.api.Test;
import org.springframework.beans.BeansException;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.test.context.ContextConfiguration;

@SpringBootTest
@ContextConfiguration(classes = CommnunityApplication.class) //启用CommunityApplication作为配置类
class CommnunityApplicationTests implements ApplicationContextAware {

    private ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

    @Test
    public void testApplicationContext() {
        System.out.println(applicationContext);

        AlphaDao alphaDao = applicationContext.getBean(AlphaDao.class);
        System.out.println(alphaDao.select());
    }
}

运行测试程序

当有两个类实现同一个接口，需要再使用的类添加@Primary注解

package com.newcoder.community.dao;

import org.springframework.context.annotation.Primary;
import org.springframework.stereotype.Repository;

@Repository
@Primary
public class AlphaMybatisImpel implements AlphaDao{

    @Override
    public String select() {
        return "Mybatis";
    }
}

或者修改bean名字

@Repository("alphaHibernate")

alphaDao = applicationContext.getBean("alphaHibernate",AlphaDao.class);
        System.out.println(alphaDao.select());

bean的初始化与销毁

创建Service包

package com.newcoder.community.service;

import com.newcoder.community.dao.AlphaDao;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import java.security.PublicKey;

@Service
public class AlphaService {
    public AlphaService() {
        System.out.println("实例化AlphaService");
    }

    @PostConstruct
    public void init() {
        System.out.println("初始化AlphaService");
    }

    @PreDestroy
    public void destroy() {
        System.out.println("销毁AlphaService");
    }
}

单独写一个测试方法

 @Test
    public void testBeanManagement() {
        AlphaService alphaService = applicationContext.getBean(AlphaService.class);
        System.out.println(alphaService);
    }

运行

注意：默认为单例模式(singleton) 若要改成多例模式需要加入在Service@scope（“prototype”）注解

配置第三方Bean

创建Config包

package com.newcoder.community.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import java.text.SimpleDateFormat;
@Configuration
public class AlphaConfig {

    @Bean
    public SimpleDateFormat singleDateFormat() {
        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    }
}

再写一个测试方法

 @Test
    public void testBeanConfig() {
        SimpleDateFormat simpleDateFormat = applicationContext.getBean(SimpleDateFormat.class);
        System.out.println(simpleDateFormat.format(new Date()));
    }

运行

依赖注入

@Autowired
    @Qualifier("alphaHibernate")
    private AlphaDao alphaDao;

    @Autowired
    private AlphaService alphaService;

    @Autowired
    private SimpleDateFormat simpleDateFormat;

    @Test
    public void testDI() {
        System.out.println(alphaDao);
        System.out.println(alphaService);
        System.out.println(simpleDateFormat);
    }

依赖注入整合

浏览器通过controller发球请求，service处理业务，dao与数据库交互返回数据
service中注入dao，通过find方法获取dao的数据

 @Autowired
    private AlphaDao alphaDao;
    
    public String find() {
        return alphaDao.select();
    }

在controller中获取service返回的数据

 @Autowired
    private AlphaService alphaService;
    
    @RequestMapping("/data")
    @ResponseBody
    public String getData() {
        return alphaService.find();
    }

打开http://localhost:8081/community/alpha/data