一、創(chuàng)建項目
此時不需要關注這是個spring boot項目，就按照java項目創(chuàng)建。
1、外層創(chuàng)建一個空項目，不用勾選；
2、刪除src目錄；
3、創(chuàng)建四個模塊，都選擇quickstart，包括web模塊也是；
- boot-common
- boot-core
- boot-dao
- boot-web
4、打開右側Maven Project，如果有某層是灰度顯示的話
右鍵Model，選擇Add FrameWork Support...
勾選上Maven即可
5、配置依賴關系
common ---> dao ---> core ---> web
web依賴core層，core層依賴dao層，dao依賴common層。
二、基礎配置
1、首先是外層pom.xml
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.9.RELEASE</version>
<relativePath/>
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
2、其次是boot-web層配置，這里邊要加上構建的配置
<build>
<finalName>boot</finalName>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<mainClass>cn.amos.web.BootWebApplication</mainClass>
<layout>ZIP</layout>
</configuration>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
3、創(chuàng)建WebApplication類，設置main啟動
@SpringBootApplication
public class BootWebApplication {
public static void main(String[] args) {
SpringApplication.run(BootWebApplication.class, args);
}
}
4、添加Controller，測試demo
@RestController
public class HelloController {
@RequestMapping("hello")
public String sayHello() {
return "Hello Spring boot!";
}
}
5、web層resources里添加application.yml
server:
port: 8085
context-path: /boot
最后測下吧 http://127.0.0.1:8085/boot/hello
三、簡單邏輯
需求：在web層的controller里邊打印一句core層返回的話
========== HelloBusiness.java ======================================================
public interface HelloBusiness {
/**
* say hello
*
* @return String
*/
String sayHello();
}
=========== HelloBusinessImpl.java ==================================================
@Component("helloBusiness")
public class HelloBusinessImpl implements HelloBusiness {
@Override
public String sayHello() {
return this.getClass().getSimpleName() + " Say Hello!";
}
}
========== HelloController.java =====================================================
@RestController
public class HelloController {
@Resource
private HelloBusiness helloBusiness;
@RequestMapping("hello")
public String sayHello() {
return helloBusiness.sayHello();
}
}
===================================================================================
按照以前的思維，這樣寫是對的
但是：運行的時候報錯
A component required a bean of type ''cn.amos.core.business.HelloBusiness'' that could not be found.
怎么辦呢？
經過上時間的調試，準備在程序的入口WebApplication上入手
加上兩個注解搞定，實現(xiàn)沒問題，具體細節(jié)呢，詳見文末。
@Configuration
@ComponentScan("cn.amos")
@Configuration
@ComponentScan("cn.amos")
@SpringBootApplication
public class BootWebApplication {
public static void main(String[] args) {
SpringApplication.run(BootWebApplication.class, args);
}
}
四、測試運行
http://127.0.0.1:8085/boot/hello
五、注解備注：
1、@Configuration
聲明當前類是一個配置類
2、@ComponentScan
使用方式如下：
@ComponentScan("cn.amos")
3、@ComponentScans
使用方式如下：
@ComponentScans({@ComponentScan("cn.amos.core"), @ComponentScan("cn.amos.dao")})
4、@SpringBootApplication
@SpringBootApplication = @Configuration + @EnableAutoConfiguration + @ComponentScan
局限性：@SpringBootApplication里的@ComponentScan只能自動掃描當前包下所有使用@Service、@Component、@Repository和@Controller的類，并注冊為bean。
所以為了掃描到其他模塊下聲明的bean，我們需要從WebApplication類入手，有以下三種實現(xiàn)方式：
我們需要掃描 boot-dao | boot-core | boot-web三層,
拿到使用@Component(@Service/@Repository/@Controller)注解的類.
====================================================================
1.自我推薦方式,類不會被重復加載,沒有用到默認的 @SpringBootApplication
這是一種捷徑吧,包名一般都是cn.amos.*.*的,所以cn.amos能掃描所有類.
@Configuration
@ComponentScan("cn.amos")
@EnableAutoConfiguration
public class BootWebApplication {
public static void main(String[] args) {
SpringApplication.run(BootWebApplication.class, args);
}
}
====================================================================
2.這種方式配置@ComponentScans,類也不會被重復加載,相對配置多了點
@Configuration
@ComponentScans({@ComponentScan("cn.amos.core"), @ComponentScan("cn.amos.dao")})
@SpringBootApplication
public class BootWebApplication {
public static void main(String[] args) {
SpringApplication.run(BootWebApplication.class, args);
}
}
====================================================================
3.這種方式看起來簡單,但是web層的bean被加載了兩次,這就不好了
@Configuration
@ComponentScan("cn.amos")
@SpringBootApplication
public class BootWebApplication {
public static void main(String[] args) {
SpringApplication.run(BootWebApplication.class, args);
}
}
感謝閱讀，不當之處，望多多指教
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