SpringBoot应用使用自定义的ApplicationContext实现类
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为什么要自定义application context
- 在学习spring容器初始化的过程中,发现spring容器预留了一些扩展点,我们可以写子类来做功能扩展,例如AbstractApplicationContext类的initPropertySources、postProcessBeanFactory、onRefresh等方法都是空方法,留给子类来扩展用;
在传统spring框架下的扩展方式
- 传统的spring框架下使用哪个ApplicationContext实现类,是自己写代码来指定的,下面是基于spring框架的应用的启动代码:
public static void main(String[] args) ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:applicationContext.xml"); Simple bean = context.getBean(Simple.class); bean.execute(); context.close();
- 如果我们要用自定的ApplicationContext实现类,只要将上面的ClassPathXmlApplicationContext改成我们做的类即可;
探寻SpringBoot框架下的扩展方式
-
先看一段代码,以下是一个SpringBoot应用启动的代码:
@SpringBootApplication public class CustomizeapplicationcontextApplication public static void main(String[] args) SpringApplication springApplication = new SpringApplication(CustomizeapplicationcontextApplication.class); springApplication.run(args);
- 从上述代码可知,我们需要去查看SpingApplication的run方法源码,那里应该有ApplicationContext初始化相关的信息,在SpingApplication的run方法中,果然找到了有用信息,如下图红框所示,是createApplicationContext方法创建了ApplicationContext实现类:
- 去看看createApplicationContext方法,如下图:
- 上图中有两点需要注意:
- 红框中显示,ApplicationContext实现类来自成员变量applicationContextClass,只要我们能设置成员变量applicationContextClass,就达到了目的:在应用中使用自定义的ApplicationContext实现类;
- 绿框中显示,如果没有设置成员变量applicationContextClass,就把AnnotationConfigServletWebServerApplicationContext作为ApplicationContext实现类,用在spring环境中,所以,我们在自定义ApplicationContext实现类时,用AnnotationConfigServletWebServerApplicationContext作为父类最合适(除了我们自己扩展的东西,其他部分都和默认的保持一致);
如何设置自定义的ApplicationContext实现类
-
从createApplicationContext方法可以看出,设置了成员变量applicationContextClass,就达到了使用自定义ApplicationContext实现类的目的,那么如何设置成员变量applicationContextClass呢?就在下面这个setApplicationContextClass方法:
public void setApplicationContextClass( Class<? extends ConfigurableApplicationContext> applicationContextClass) this.applicationContextClass = applicationContextClass; if (!isWebApplicationContext(applicationContextClass)) this.webApplicationType = WebApplicationType.NONE;
-
我们只要在启动应用的时候,在调用springApplication的run方法之前先调用setApplicationContextClass方法就能指定ApplicationContext实现类了;
- 分析到此,您是否和我一样有疑虑:setApplicationContextClass方法会不会被在其他地方被调用,导致我们的设置无效呢?通过以下两种方法来检查:
- 在IntelliJ IDEA中,通过"Find Usages"的方式查找该方法被调用的地方,结果只发现了一处SpringBootServletInitializer类的onStartup方法,这是war包形式的应用在配置Initializer的时候才会用到,main方法启动的方式中不会用到;
- 在setApplicationContextClass方法中打断点,debug启动应用,确认不会走进来;
实战使用自定义的ApplicationContext实现类
- 理论分析完毕,可以实战验证了:
-
基于maven创建一个SpringBoot的web应用,pom.xml如下:
<?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.bolingcavalry</groupId> <artifactId>customizeapplicationcontext</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>customizeapplicationcontext</name> <description>Demo project for Spring Boot</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.4.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </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> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
- 创建类CustomizeApplicationContext,继承自AnnotationConfigServletWebServerApplicationContext,重写了父类的几个方法,如下:
package com.bolingcavalry.customizeapplicationcontext;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext;
/**
- @Description : 自定义的ApplicationContext实现类
- @Author : zq2599@gmail.com
-
@Date : 2018-08-11 17:12
*/
public class CustomizeApplicationContext extends AnnotationConfigServletWebServerApplicationContextLog logger = LogFactory.getLog(CustomizeApplicationContext.class);
@Override
protected void initPropertySources()
super.initPropertySources();
logger.info("execute override initPropertySources");@Override
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
super.postProcessBeanFactory(beanFactory);
logger.info("execute override postProcessBeanFactory");@Override
protected void onRefresh()
super.onRefresh();
logger.info("execute override onRefresh");
- 启动类CustomizeapplicationcontextApplication的main方法中,调用setApplicationContextClass方法,将ApplicationContext实现类设置为CustomizeApplicationContext:
```java
package com.bolingcavalry.customizeapplicationcontext;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class CustomizeapplicationcontextApplication
public static void main(String[] args)
SpringApplication springApplication = new SpringApplication(CustomizeapplicationcontextApplication.class);
springApplication.setApplicationContextClass(CustomizeApplicationContext.class);
springApplication.run(args);
- 启动应用,查看日志如下,CustomizeApplicationContext中重写的方法都被执行了,并且initPropertySources被执行了两次,那是因为除了AbstractApplicationContext类中有调用,在ServletWebServerApplicationContext类的onRefresh中会执行createWebServer方法,而createWebServer方法中也会调用一次initPropertySources方法:
2018-08-11 17:21:18.833 INFO 5132 --- [ main] c.CustomizeapplicationcontextApplication : Starting CustomizeapplicationcontextApplication on zhaoqinwin10 with PID 5132 (D:\\temp\\201808\\09\\customizeapplicationcontext\\target\\classes started by 12167 in D:\\temp\\201808\\09\\customizeapplicationcontext) 2018-08-11 17:21:18.840 INFO 5132 --- [ main] c.CustomizeapplicationcontextApplication : No active profile set, falling back to default profiles: default 2018-08-11 17:21:18.957 INFO 5132 --- [ main] c.b.c.CustomizeApplicationContext : Refreshing com.bolingcavalry.customizeapplicationcontext.CustomizeApplicationContext@5906ebcb: startup date [Sat Aug 11 17:21:18 CST 2018]; root of context hierarchy 2018-08-11 17:21:18.958 INFO 5132 --- [ main] c.b.c.CustomizeApplicationContext : execute override initPropertySources 2018-08-11 17:21:18.967 INFO 5132 --- [ main] c.b.c.CustomizeApplicationContext : execute override postProcessBeanFactory 2018-08-11 17:21:20.085 INFO 5132 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http) 2018-08-11 17:21:20.102 INFO 5132 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat] 2018-08-11 17:21:20.103 INFO 5132 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/8.5.32 2018-08-11 17:21:20.106 INFO 5132 --- [ost-startStop-1] o.a.catalina.core.AprLifecycleListener : The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: [C:\\jdk\\bin;C:\\WINDOWS\\Sun\\Java\\bin;C:\\WINDOWS\\system32;C:\\WINDOWS;C:\\ProgramData\\Oracle\\Java\\javapath;C:\\Program Files (x86)\\Intel\\iCLS Client\\;C:\\Program Files\\Intel\\iCLS Client\\;C:\\Windows\\system32;C:\\Windows;C:\\Windows\\System32\\Wbem;C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\;C:\\Program Files (x86)\\Intel\\Intel(R) Management Engine Components\\DAL;C:\\Program Files\\Intel\\Intel(R) Management Engine Components\\DAL;C:\\Program Files (x86)\\Intel\\Intel(R) Management Engine Components\\IPT;C:\\Program Files\\Intel\\Intel(R) Management Engine Components\\IPT;C:\\Program Files (x86)\\NVIDIA Corporation\\PhysX\\Common;C:\\Program Files\\Intel\\WiFi\\bin\\;C:\\Program Files\\Common Files\\Intel\\WirelessCommon\\;C:\\software\\apache-maven-3.3.3\\bin\\;C:\\software\\Git\\bin;E:\\work\\dubbo\\zookeeper-3.3.6/bin;E:\\work\\dubbo\\zookeeper-3.3.6/conf;D:\\soft\\gradle-1.1\\bin;C:\\jdk\\bin;C:\\software\\svn\\bin;D:\\software\\androidSdk\\platform-tools;D:\\software\\calibre\\;D:\\software\\gradle-2.14.1\\bin;C:\\WINDOWS\\system32;C:\\WINDOWS;C:\\WINDOWS\\System32\\Wbem;C:\\WINDOWS\\System32\\WindowsPowerShell\\v1.0\\;C:\\Program Files\\Git\\cmd;C:\\Users\\12167\\AppData\\Local\\Microsoft\\WindowsApps;C:\\Users\\12167\\AppData\\Local\\Programs\\Fiddler;%USERPROFILE%\\AppData\\Local\\Microsoft\\WindowsApps;.] 2018-08-11 17:21:20.226 INFO 5132 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext 2018-08-11 17:21:20.227 INFO 5132 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1273 ms 2018-08-11 17:21:20.305 INFO 5132 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean : Servlet dispatcherServlet mapped to [/] 2018-08-11 17:21:20.310 INFO 5132 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: characterEncodingFilter to: [/*] 2018-08-11 17:21:20.310 INFO 5132 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: hiddenHttpMethodFilter to: [/*] 2018-08-11 17:21:20.310 INFO 5132 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: httpPutFormContentFilter to: [/*] 2018-08-11 17:21:20.310 INFO 5132 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: requestContextFilter to: [/*] 2018-08-11 17:21:20.330 INFO 5132 --- [ main] c.b.c.CustomizeApplicationContext : execute override initPropertySources 2018-08-11 17:21:20.330 INFO 5132 --- [ main] c.b.c.CustomizeApplicationContext : execute override onRefresh
实战源码下载
- 本章实战的源码可以在github下载,地址和链接信息如下表所示:
名称 | 链接 | 备注 |
---|---|---|
项目主页 | https://github.com/zq2599/blog_demos | 该项目在GitHub上的主页 |
git仓库地址(https) | https://github.com/zq2599/blog_demos.git | 该项目源码的仓库地址,https协议 |
git仓库地址(ssh) | git@github.com:zq2599/blog_demos.git | 该项目源码的仓库地址,ssh协议 |
-
这个git项目中有多个文件夹,本章源码在文件夹customizeapplicationcontext下,如下图红框所示:
- 至此,我们通过查看SpringApplication的源码,搞清楚了spring环境的ApplicationContext实现类在SpringBoot框架下如何指定,也做了一次简单的自定义实战,今后在研究和学习spring过程中,如果需要扩展spring容器就能在SpringBoot环境下进行了,相比传统的war包部署、以及指定多个jar包的classpath等操作,springboot应用的单个jar包更方便省事。
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