spring实战学习笔记（一）spring装配bean

最近在学习spring boot 发现对某些注解不是很深入的了解。看技术书给出的实例会很疑惑为什么要用这个注解？这个注解的作用？有其他相同作用的注解吗？这个注解的运行机制是什么？等等 springboot 相对spring 改变了些规则和使用方式。总感觉还是需要把springboot的祖先了解下。

买了本spring 实战4 希望对我的了解有帮助。

spring 的出现代替了更加重量级的企业java技术，相对EJB 它提供了简单的编程和轻量级。

一 spring bean java配置

环境：java version "1.8.0_181" tomcat 8.0

spring 框架jar包下载 http://repo.spring.io/release/org/springframework/spring/

在eclipse 新建项目导入spring基础jar

创建实体类：

1 package soundsystem;
2 
3 import org.springframework.context.annotation.ComponentScan;
4 import org.springframework.context.annotation.Configuration;
5 import org.junit.Test;
6 @Configuration
7 @ComponentScan(basePackages= {"com.lzl.spring.test","soundsystem"})
8 public class CDPlayerConfig {
9 }

package com.lzl.spring.test;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import soundsystem.CDPlayerConfig;
import soundsystem.SgtPeppers;
public class TestCD {

@Test
public void play() {

AnnotationConfigApplicationContext applicationContext2 = new AnnotationConfigApplicationContext(CDPlayerConfig.class);
  SgtPeppers bean = (SgtPeppers) applicationContext2.getBean("sgtPeppers");
  if(bean!= null) {
   bean.play();
  }else {
   System.out.println("beanis null");
  }
}

但是一直报错：No tests found matching [{ExactMatcher:fDisplayName=play], {ExactMatcher:fDisplayName=play(com.lzl.spring.test.TestCD)], {LeadingIdentifierMatcher:fClassName=com.lzl.spring.test.TestCD,fLeadingIdentifier=play]] from org.junit.internal.requests.ClassReques

也没有详细的报错信息，之后把测试内容放在了main方法里面

 1 package com.lzl.spring.test;
 2 
 3 
 4 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 5 
 6 import soundsystem.CDPlayerConfig;
 7 import soundsystem.SgtPeppers;
 8 public class TestCD {
 9 
10     
11     public static void main(String[] args) {
12          AnnotationConfigApplicationContext applicationContext2 = new AnnotationConfigApplicationContext(CDPlayerConfig.class);
13         SgtPeppers bean = (SgtPeppers) applicationContext2.getBean("sgtPeppers");
14         
15 if(bean != null) {
16             bean .play();
17         }else {
18             System.out.println("bean is null");
19         }
20 
21         
22     }
23

运行结果抛

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory
at org.springframework.context.support.AbstractApplicationContext.<init>(AbstractApplicationContext.java:153)
at org.springframework.context.support.GenericApplicationContext.<init>(GenericApplicationContext.java:100)
at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:60)
at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:82)
at com.lzl.spring.test.TestCD.main(TestCD.java:13)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 5 more

最后下载了 apache-common-logging ：http://commons.apache.org/proper/commons-logging/download_logging.cgi 放入项目lib包下构建了运行成功