docker java開發環境，使用Spring容器最簡單的代碼姿勢

如果僅僅是為了測試簡單使用一下Spring的IOC容器，或者研究一下Spring的容器的源碼實現，那么在搭建Spring工程的時候，不需要復雜的xml配置。Spring3.0之后提供了Java注解配置的方式來啟動Spring容器。下面是最簡單的啟動Spring容器的方式：

1.依賴包只需要spring-context即可：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.springexample</groupId><artifactId>spring-ioc</artifactId><version>1.0-SNAPSHOT</version><dependencies><dependency><groupId>org.springframework</groupId><artifactId>spring-context</artifactId><version>5.1.8.RELEASE</version></dependency></dependencies></project>

2.一個啟動測試類：

import com.spring.ioc.SpringConfig;
import com.spring.ioc.UserService;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class Application {public static void main(String[] args) {AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);UserService userService = context.getBean(UserService.class);System.out.println(userService.getSysUser());}
}

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3.一個配置類（@Configuration注解的類相當于一個xml文件），用于掃描和注冊Bean，@ComponentScan注解用于要掃描哪個包下的Bean（即掃描@Service、@Repository等注解的Bean）：

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;@ComponentScan("com.spring")
@Configuration
public class SpringConfig {}

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4.模擬一個業務類，類上加上@Service注解：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;@Service
public class UserService {@Autowiredprivate UserDao userDao;public SysUser getSysUser() {return userDao.getSysUser();}
}

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5.模擬Dao服務，類上加上@Repository注解，提供數據訪問服務：

import org.springframework.stereotype.Repository;@Repository
public class UserDao {public SysUser getSysUser() {SysUser sysUser = new SysUser();sysUser.setUserId(2);sysUser.setUserName("Tom");return sysUser;}
}

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6.一個實體類，用于封裝業務數據：

public class SysUser {private Integer userId;private String userName;public Integer getUserId() {return userId;}public void setUserId(Integer userId) {this.userId = userId;}public String getUserName() {return userName;}public void setUserName(String userName) {this.userName = userName;}@Overridepublic String toString() {return "SysUser{" +"userId=" + userId +", userName='" + userName + '\'' +'}';}
}

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6.執行測試類Application中的main方法，查看輸出結果：

SysUser{userId=2, userName='Tom'}

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