1. 准备:了解基本概念、规划实战内容;
2. 实战:开发自定义starter,并在demo工程中使用它;
3. 深入:从spring和spring boot源码层面分析starter的原理;
RequestContextHolder.setRequestAttributes(new
ServletRequestAttributes(req));
//MvcUriComponentsBuilder类似于ServletUriComponentsBuilder,但是直接从控制器
获取
//类级别的
System.out.println(
fromController(UserController.class).build().toString()
);
//方法级别的
System.out.println(
fromMethodName(UserController.class, "view",
1L).build().toString()
);
//通过Mock方法调用得到
System.out.println(
fromMethodCall(on(UserController.class).getUser(2L)).build()
);
}
}本章内容概览
1. 查看官方资料;
2. 设定实战目标;
3. 学习spring cloud的starter,作为实战参考;
4. 实战内容的具体设计;
版本信息
本次实战的版本信息:
1. java:1.8.0_144
2. spring boot:1.5.16.RELEASE
3. spring cloud:Edgware.RELEASE
官方资料
为了有个初始印象,我们从spring官方文档看起吧:
1. 官网:https://spring.io/docs/reference,点击下图红框位置:2. 在弹出的列表中选择1.5.16版本的reference,如下图红框:
3. 在打开的文档目录中很容易找到starter的章节,地址是:https://docs.spring.io/spring-boot/doc
s/1.5.16.RELEASE/reference/htmlsingle/#using-boot-starter,内容如下图:
我的理解:
第一. 在应用中可以用starter将依赖库问题变得简单,如果你想依赖Spring和JPA,只需在应用中依赖
spring-boot-starter-data-jpa即可;
第二. 常用库的官方starter,其artifactId的格式类似"spring-boot-starter-*", 对于非官方的starter,
建议将业务名称放在"spring-boot-starter"前面,例如"acme-spring-boot-starter";
第三. 已列举常用的官方starter,可用来参考;设定实战目标
本次实战的目标如下:
1. A应用提供加法计算的服务;
2. B应用提供减法计算的服务;
3. C应用要使用加法计算和减法计算的服务,并且减法服务可以通过配置来实现是否支持负数;
学习spring cloud的starter
目标已定下,但是先不急着编码,我们去看下spring cloud的设计,用来作为借鉴参考;
回顾一下我们使用Spring cloud的时候,如果要把一个应用作为Eureka client注册到Eureka server,只
需在应用的pom.xml中添加如下依赖:
注册到Eureka server的工作,是由CloudEurekaClient类完成的,该类属于模块spring-cloud-netflix
eureka-client,因此我们要弄清楚以下两点:
1. 为什么不需要应用的pom.xml中依赖spring-cloud-netflix-eureka-client?
2. 为什么应用能自动注册到Eureka sever?
如何建立对spring-cloud-netflix-eureka-client模块的依赖
打开spring-cloud-starter-netflix-eureka-client模块的pom.xml文件就一目了然了,如下图,原来在这
个pom.xml文件中已经依赖了spring-cloud-netflix-eureka-client模块,因此,我们的应用只需依赖
spring-cloud-starter-netflix-eureka-client模块,就能间接依赖到spring-cloud-netflix-eureka-client模
块:
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>再看看上图中其他的依赖,可以发现的确如官方文档所说,starter处理了复杂的依赖关系,我们只需要
依赖starter即可,官方文档中还有一段话需要注意,如下图:上图红框中说明starter是个空的jar,其作用就是用来提供必要的模块依赖的,来看看spring-cloud
starter-netflix-eureka-client模块是否遵守此规则,如下图,只有配置文件,没有任何class:
为什么应用能自动注册到Eureka sever
作为Eureka client的应用,在启动后就自动注册到Eureka server了,作为应用开发者的我们除了在
pom.xml中依赖spring-cloud-starter-netflix-eureka-client模块,没有做其他设置,这是如何实现的
呢?
1. 注册到Eureka server的工作,是CloudEurekaClient类在其父类的构造方法中完成的,搜索源码发
现此类的在EurekaClientAutoConfiguration中被注册到spring容器,如下图红框所示:
所以,现在问题就变成了如何让EurekaClientAutoConfiguration类被实例化?
1. 在spring-cloud-netflix-eureka-client模块的spring.factories文件中,找到了
EurekaClientAutoConfiguration:模块名称
作用
备注
customizeapi
包含
了接口
和异常
的定义
实现和调用服务时用到的接口和异常都在此工程中
addservice
提供加
法服务
普通的maven工程,里面加法接口的实现类
minusservice
提供减
法服务
普通的maven工程,里面有两个减法接口的实现类,一
个支持负数,另一个不支持
customizeservicestarter
自定义
starter
模块
pom.xml中依赖了customizeapi、addservice、
minusservice,自身有个Configuration类,通过@Bean
注解向spring容器注册AddService和MinusService的实
例
这是个spring boot的扩展配置,在此文件中配置的bean都会被实例化,然后注册到spring容器,具体的
细节,我们会在第三章结合spring boot源码详细分析,本章只要知道用法即可;
此处小结Eureka client自动注册到Eureka server的过程:
第一、spring-cloud-netflix-eureka-client模块的spring.factories文件中配置了
EurekaClientAutoConfiguration,因此EurekaClientAutoConfiguration会被实例化并注册到Spring容
器中;
第二、EurekaClientAutoConfiguration中配置了CloudEurekaClient,因此CloudEurekaClient会实例
化,在构造方法中执行了注册;
实战的设计
参考了spring cloud的starter设计后,接下来的实战被设计成两个maven工程:customizestarter和
customizestartertestdemo;
1. 工程customizestarter里面包含了四个模块,每个模块功能如下所示:1. 工程customizestartertestdemo在pom.xml中依赖了上述的customizeservicestarter模块,提供
的web服务会用到addservice和minusservice的服务,并且在应用启动时设置环境变量来选择使用
的减法服务是否支持负数;
至此,准备工作已经完成了,对基本原理和开发设计都已经清楚,接下来的章节我们来一起开发上述五
个工程;
自定义spring boot starter三部曲之二:实战开发
本文是《自定义spring boot starter三部曲》的第二篇,上一篇中我们通过学习spring cloud的starter,
对spring boot的starter有了初步了解,也设计好了实战内容,今天就来一起实现;
本章内容概述
1. 创建工程customizestarter;
2. 创建模块customizeapi;
3. 创建模块addservice;
4. 创建模块minusservice;
5. 创建模块customizeservicestarter;
6. 构建工程customizestarter,并安装到本地maven仓库;
7. 创建工程customizestartertestdemo;
8. 构建工程customizestartertestdemo,得到jar包;
9. 启动customizestartertestdemo工程的jar包,并带上一个启动参数,验证支持负数的减法服务;
10. 启动customizestartertestdemo工程的jar包,验证不支持服务的减法服务;
创建工程customizestarter
1. 创建一个名为customizestarter的maven工程,以spring-boot-starter-parent作为父工程,同时自
身又是后续几个模块的父工程,pom.xml内容如下:
<?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>customizestarter</artifactId>
<packaging>pom</packaging>
<version>0.0.1-SNAPSHOT</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>创建模块customizeapi
1. 在工程customizestarter下创建模块customizeapi,这是个java工程,里面是加法和减法服务的接
口,和一个业务异常的定义;
2. customizeapi的pom.xml内容如下,很简单,只有基本定义:
1. 异常定义类:
1. 加法服务的接口类AddService:
<version>1.5.9.RELEASE</version>
<relativePath/>
</parent>
<modules>
<!--加法服务-->
<module>addservice</module>
<!--减法服务-->
<module>minusservice</module>
<!--接口和异常定义-->
<module>customizeapi</module>
<!--启动器-->
<module>customizeservicestarter</module>
</modules>
</project>
<?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">
<parent>
<artifactId>customizestarter</artifactId>
<groupId>com.bolingcavalry</groupId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../</relativePath>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>customizeapi</artifactId>
</project>
package com.bolingcavalry.api.exception;
/**
* @author wilzhao
* @description 执行减法服务时抛出的异常
* @email zq2599@gmail.com
* @time 2018/10/13 14:20
*/
public class MinusException extends Exception{
public MinusException(String message) {
super(message);
}
}1. 减法服务定义类,注意减法API声明了异常抛出,因为如果已经配置了不支持负数的减法服务,那
么被减数如果小于减数就抛出异常:
创建模块addservice
1. 在工程customizestarter下创建模块addservice,这是个java工程,里面包含了加法相服务的实
现,pom.xml内容如下,注意由于要实现加法接口,因此需要依赖模块customizeapi:
package com.bolingcavalry.api.service;
/**
* @author wilzhao
* @description 加法服务对应的接口
* @email zq2599@gmail.com
* @time 2018/10/13 10:07
*/
public interface AddService {
/**
* 普通加法
* @param a
* @param b
* @return
*/
int add(int a, int b);
}
package com.bolingcavalry.api.service;
import com.bolingcavalry.api.exception.MinusException;
/**
* @author wilzhao
* @description 减法服务
* @email zq2599@gmail.com
* @time 2018/10/13 12:07
*/
public interface MinusService {
/**
* 普通减法
* @param minuend 减数
* @param subtraction 被减数
* @return 差
*/
int minus(int minuend, int subtraction) throws MinusException;
}
<?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">
<parent>
<artifactId>customizestarter</artifactId>
<groupId>com.bolingcavalry</groupId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../</relativePath>1. 加法接口的实现类AddServiceImpl很简单,如下:
创建模块minusservice
1. 在工程customizestarter下创建模块minusservice,这是个java工程,里面包含了减法相服务的实
现,pom.xml内容如下,注意由于要实现减法接口,因此需要依赖模块customizeapi:
</parent>
<artifactId>addservice</artifactId>
<modelVersion>4.0.0</modelVersion>
<dependencies>
<dependency>
<groupId>com.bolingcavalry</groupId>
<artifactId>customizeapi</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
</project>
package com.bolingcavalry.addservice.service.impl;
import com.bolingcavalry.api.service.AddService;
/**
* @author wilzhao
* @description 加法服务的实现
* @email zq2599@gmail.com
* @time 2018/10/13 10:59
*/
public class AddServiceImpl implements AddService {
public int add(int a, int b) {
return a + b;
}
}
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>customizestarter</artifactId>
<groupId>com.bolingcavalry</groupId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../</relativePath>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>minusservice</artifactId>
<dependencies>
<dependency>
<groupId>com.bolingcavalry</groupId>
<artifactId>customizeapi</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies></project>
1. 一共有两个减法接口的实现类,第一个不支持负数结果,如果被减数小于减数就抛出异常
MinusException:
package com.bolingcavalry.minusservice.service.impl;
import com.bolingcavalry.api.exception.MinusException;
import com.bolingcavalry.api.service.MinusService;
/**
* @author wilzhao
* @description 减法服务的实现,不支持负数
* @email zq2599@gmail.com
* @time 2018/10/13 14:24
*/
public class MinusServiceNotSupportNegativeImpl implements MinusService {
/**
* 减法运算,不支持负数结果,如果被减数小于减数,就跑出MinusException
* @param minuend 被减数
* @param subtraction 减数
* @return
* @throws MinusException
*/
public int minus(int minuend, int subtraction) throws MinusException {
if(subtraction>minuend){
throw new MinusException("not support negative!");
}
return minuend-subtraction;
}
}
1. 第二个减法接口的实现类支持负数返回:
package com.bolingcavalry.minusservice.service.impl;
import com.bolingcavalry.api.exception.MinusException;
import com.bolingcavalry.api.service.MinusService;
/**
* @author wilzhao
* @description 支持负数结果的减法服务
* @email zq2599@gmail.com
* @time 2018/10/13 14:30
*/
public class MinusServiceSupportNegativeImpl implements MinusService {
/**
* 减法实现,支持负数
* @param minuend 减数
* @param subtraction 被减数
* @return
* @throws MinusException
*/创建模块customizeservicestarter
1. 在工程customizestarter下创建模块customizeservicestarter,这是个java工程,里面需要依赖
spring boot配置相关的库,由于要在配置中实例化加法和减法服务的实现,因此customizeapi、
addservice、minusservice这些模块都要在pom.xml中声明依赖,如下:
1. 创建配置类CustomizeConfiguration,注意getSupportMinusService和
getNotSupportMinusService这两个方法上的注解配置,如果环境变量
com.bolingcavalry.supportnegative存在并且等于true,那么getSupportMinusService方法就返
回了MinusService接口的实例,如果当前环境没有MinusService接口的实例,就由
getNotSupportMinusService方法就返回一个,并且有会在控制台打印创建了哪种实现:
public int minus(int minuend, int subtraction) throws MinusException {
return minuend - subtraction;
}
}
<?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">
<parent>
<artifactId>customizestarter</artifactId>
<groupId>com.bolingcavalry</groupId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../</relativePath>
</parent>
<artifactId>customizeservicestarter</artifactId>
<modelVersion>4.0.0</modelVersion>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-autoconfigure</artifactId>
<!--仅编译时才需要-->
<scope>provided</scope>
</dependency>
<dependency>
<groupId>com.bolingcavalry</groupId>
<artifactId>customizeapi</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>com.bolingcavalry</groupId>
<artifactId>addservice</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>com.bolingcavalry</groupId>
<artifactId>minusservice</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
</project>package com.bolingcavalry.customizeservicestarter;
import com.bolingcavalry.addservice.service.impl.AddServiceImpl;
import com.bolingcavalry.api.service.AddService;
import com.bolingcavalry.api.service.MinusService;
import
com.bolingcavalry.minusservice.service.impl.MinusServiceNotSupportNegativeImpl;
import
com.bolingcavalry.minusservice.service.impl.MinusServiceSupportNegativeImpl;
import org.springframework.beans.factory.annotation.Qualifier;
import
org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
/**
* @author wilzhao
* @description 一句话介绍
* @email zq2599@gmail.com
* @time 2018/10/13 14:36
*/
@Configuration
public class CustomizeConfiguration {
@Bean
public AddService getAddService(){
System.out.println("create addService");
return new AddServiceImpl();
}
/**
* 如果配置了com.bolingcavalry.supportnegative=true,
* 就实例化MinusServiceSupportNegativeImpl
* @return
*/
@Bean
@ConditionalOnProperty(prefix="com.bolingcavalry",name = "supportnegative",
havingValue = "true")
public MinusService getSupportMinusService(){
System.out.println("create minusService support minus");
return new MinusServiceSupportNegativeImpl();
}
/**
* 如果没有配置com.bolingcavalry.supportnegative=true,
* 就不会实例化MinusServiceSupportNegativeImpl,
* 这里的条件是如果没有MinusService类型的bean,就在此实例化一个
* @return
*/
@Bean
@ConditionalOnMissingBean(MinusService.class)
public MinusService getNotSupportMinusService(){
System.out.println("create minusService not support minus");
return new MinusServiceNotSupportNegativeImpl();
}
}1. 在src\main\resources目录下创建一个目录META-INF,里面创建一个文件spring.factories,内容
是如下,表示如果当前应用支持spring boot的自动配置,就会被spring boot框架实例化并注册到
spring容器内:
构建工程customizestarter
1. 到这里customizestarter工程的编码就结束了,在工程内pom.xml所在目录(也就是
customizestarter内的第一层目录),执行以下命令可以编译构建并安装到本地maven仓库:
1. 如果编译构建和安装都成功了,可以看到类似如下输出:
现在starter已经准备好了,我们做一个spring boot的web应用来验证一下;
创建工程customizestartertestdemo
1. 工程customizestartertestdemo是个简单的spring boot应用,pom.xml如下,可见并无特别之
处,只是多了customizeservicestarter的依赖:
org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.bolingcavalry
.customizeservicestarter.CustomizeConfiguration
mvn clean install -Dmaven.test.skip=true -U
[INFO] Installing
C:\temp\201810\07\customizestarter\customizeservicestarter\pom.xml to
C:\Users\12167\.m2\repositor
y\com\bolingcavalry\customizeservicestarter\0.0.1-
SNAPSHOT\customizeservicestarter-0.0.1-SNAPSHOT.pom
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO]
[INFO] customizestarter ................................... SUCCESS [ 0.748 s]
[INFO] customizeapi ....................................... SUCCESS [ 3.266 s]
[INFO] addservice ......................................... SUCCESS [ 0.427 s]
[INFO] minusservice ....................................... SUCCESS [ 0.344 s]
[INFO] customizeservicestarter ............................ SUCCESS [ 0.495 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 5.954 s
[INFO] Finished at: 2018-10-14T00:17:46+08:00
[INFO] Final Memory: 29M/221M
[INFO] ------------------------------------------------------------------------
<?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>customizestartertestdemo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging><name>customizestartertestdemo</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.9.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>
<dependency>
<groupId>com.bolingcavalry</groupId>
<artifactId>customizeservicestarter</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
1. 开发一个Controller类,用于调用AddService和MinusService对应的服务:
package com.bolingcavalry.customizestartertestdemo.controller;
import com.bolingcavalry.api.exception.MinusException;
import com.bolingcavalry.api.service.AddService;
import com.bolingcavalry.api.service.MinusService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;1. 启动类如下:
构建工程customizestartertestdemo
1. 在customizestartertestdemo工程的pom.xml所在目录下执行以下命令即可构建成功:
1. 命令执行成功后,即可在target目录下见到customizestartertestdemo-0.0.1-SNAPSHOT.jar文
件,如下图:
/**
* @author wilzhao
* @description 调用加法和减法服务的测试类
* @email zq2599@gmail.com
* @time 2018/10/13 16:00
*/
@RestController
public class CalculateController {
@Autowired
private AddService addService;
@Autowired
private MinusService minusService;
@RequestMapping(value = "/add/{added}/{add}", method = RequestMethod.GET)
public String add(@PathVariable("added") int added, @PathVariable("add") int
add){
return added + " 加 " + add + " 等于 : " + addService.add(added, add);
}
@RequestMapping(value = "/minus/{minuend}/{subtraction}", method =
RequestMethod.GET)
public String minus(@PathVariable("minuend") int minuend,
@PathVariable("subtraction") int subtraction) throws MinusException {
return minuend + " 减 " + subtraction + " 等于 : " +
minusService.minus(minuend, subtraction);
}
}
package com.bolingcavalry.customizestartertestdemo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class CustomizestartertestdemoApplication {
public static void main(String[] args) {
SpringApplication.run(CustomizestartertestdemoApplication.class, args);
}
}
mvn clean package -Dmaven.test.skip=true现在编码和构建已经全部完成,我们可以来验证了;
验证支持负数的减法服务
1. 在customizeapi模块的CustomizeConfiguration类中,有如下方法和注解:
从上述代码可见,只要环境变量"com.bolingcavalry.supportnegative"等于true,注册到spring容器的
就是MinusServiceSupportNegativeImpl类的实例;
1. customizestartertestdemo-0.0.1-SNAPSHOT.jar文件所在目录下,执行以下命令启动应用:
1. 在控制台中可以看见create minusService support minus,表示注册到spring容器的是
MinusServiceSupportNegativeImpl类的实例,如下所示:
@Bean
@ConditionalOnProperty(prefix="com.bolingcavalry",name = "supportnegative",
havingValue = "true")
public MinusService getSupportMinusService(){
System.out.println("create minusService support minus");
return new MinusServiceSupportNegativeImpl();
}
java -Dcom.bolingcavalry.supportnegative=true -jar customizestartertestdemo-
0.0.1-SNAPSHOT.jar
2018-10-14 12:04:54.233 INFO 16588 --- [ost-startStop-1]
o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'requestContextFilter'
to: [/*]
create addService
create minusService support minus
2018-10-14 12:04:54.845 INFO 16588 --- [ main]
s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice:
org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplication
Context@443b7951: startup date [Sun Oct 14 12:04:50 CST 2018]; root of context
hierarchy1. 在浏览器访问http://localhost:8080/minus/1/2,可见返回计算结果为负数:
验证不支持负数的减法服务
1. 前面已经分析过,CustomizeConfiguration类的getNotSupportMinusService方法执行的条件是
环境变量"com.bolingcavalry.supportnegative"等于true,如果没有这个环境变量,
getNotSupportMinusService方法就不会执行,spring容器中就没有MinusService接口的实例;
2. CustomizeConfiguration类中,有如下方法和注解:
从上述代码可见,spring容器中如果没有MinusService接口的实例,getNotSupportMinusService方法
就会被执行,在spring容器中注册MinusServiceNotSupportNegativeImpl实例;
因此接下来的我们启动的应用如果没有环境变量"com.bolingcavalry.supportnegative",就可以使用到
不支持负数的减法服务了;
\2. 停掉之前启动的应用,然后执行以下命令启动应用:
1. 在控制台中可以看见create minusService not support minus,表示注册到spring容器的是
MinusServiceNotSupportNegativeImpl类的实例,如下所示:
1. 在浏览器访问http://localhost:8080/minus/1/2,由于MinusServiceNotSupportNegativeImpl实
例不支持负数减法,会直接抛出异常,如下图:
@Bean
@ConditionalOnMissingBean(MinusService.class)
public MinusService getNotSupportMinusService(){
System.out.println("create minusService not support minus");
return new MinusServiceNotSupportNegativeImpl();
}
java -jar customizestartertestdemo-0.0.1-SNAPSHOT.jar
2018-10-14 12:15:05.994 INFO 16608 --- [ost-startStop-1]
o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'requestContextFilter'
to: [/*]
create addService
create minusService not support minus
2018-10-14 12:15:06.592 INFO 16608 --- [ main]
s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice:
org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplication
Context@443b7951: startup date [Sun Oct 14 12:15:02 CST 2018]; root of context
hierarchy至此,自定义spring boot starter的编码实战就完成了,希望本篇可以给您用来作参考,助您做出自己
所需的starter;
下一篇我们一起去看看spring boot的源码,对这个高效的扩展功能做更深入的了解;
自定义spring boot starter三部曲之三:源码分析spring.factories加载过程
版本情况
本文中涉及到的库的版本:
1. Spring boot :1.5.9.RELEASE;
2. JDK :1.8.0_144
初步分析
先回顾customizeservicestarter模块中spring.factories文件的内容:
从上述内容可以确定今天源码学习目标:
1. spring容器如何处理配置类;
2. spring boot配置类的加载情况;
3. spring.factories中的EnableAutoConfiguration配置何时被加载?
4. spring.factories中的EnableAutoConfiguration配置被加载后做了什么处理;
spring容器如何处理配置类
1. ConfigurationClassPostProcessor类的职责是处理配置类;
2. ConfigurationClassPostProcessor是BeanDefinitionRegistryPostProcessor接口的实现类,它的
postProcessBeanDefinitionRegistry方法在容器初始化阶段会被调用;
3. postProcessBeanDefinitionRegistry方法又调用processConfigBeanDefinitions方法处理具体业
务;
org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.bolingcavalry
.customizeservicestarter.CustomizeConfiguration4. processConfigBeanDefinitions方法中通过ConfigurationClassParser类来处理Configuration注
解,如下图:
5. 如上图红框所示,所有被Configuration注解修饰过的类,都会被parser.parse(candidates)处理,
即ConfigurationClassParser类的parse方法;
6. parse方法中调用processDeferredImportSelectors方法做处理:找到Configuration类中的
Import注解,对于Import注解的值,如果实现了ImportSelector接口,就调用其selectImports方
法,将返回的名称实例化:
private void processDeferredImportSelectors() {
//这里就是Configuration注解中的Import注解的值,
//例如EnableAutoConfiguration注解的源码中,Import注解的值是
EnableAutoConfigurationImportSelector.class
List<DeferredImportSelectorHolder> deferredImports =
this.deferredImportSelectors;
this.deferredImportSelectors = null;
Collections.sort(deferredImports, DEFERRED_IMPORT_COMPARATOR);
for (DeferredImportSelectorHolder deferredImport : deferredImports) {
ConfigurationClass configClass =
deferredImport.getConfigurationClass();
try {
//以EnableAutoConfiguration注解为例,其Import注解的值为
EnableAutoConfigurationImportSelector.class,
//那么此处就是在调用EnableAutoConfigurationImportSelector的
selectImports方法,返回了一个字符串数组
String[] imports =
deferredImport.getImportSelector().selectImports(configClass.getMetadata());
//字符串数组中的每个字符串都代表一个类,此处做实例化
processImports(configClass, asSourceClass(configClass),
asSourceClasses(imports), false);
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to process import candidates for configuration
class [" +
configClass.getMetadata().getClassName() + "]", ex);
}
}
}
小结一下spring容器配置类的逻辑:
1. 找出配置类;
2. 找出配置类中的Import注解;3. Import注解的值是class,如果该class实现了ImportSelector接口,就调用其selectImports方法,
将返回的名称实例化;
有了上面的结论就可以结合Spring boot的源码来分析加载了哪些数据了;
spring boot配置类的加载情况
1. 我们的应用使用了SpringBootApplication注解,看此注解的源码,使用了
EnableAutoConfiguration注解:
2. EnableAutoConfiguration注解中,通过Import注解引入了
EnableAutoConfigurationImportSelector.class:
3. 看EnableAutoConfigurationImportSelector的源码:
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = {
@Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
@Filter(type = FilterType.CUSTOM, classes =
AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {
......
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(EnableAutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration {
......
/**
* {@link DeferredImportSelector} to handle {@link EnableAutoConfiguration
* auto-configuration}. This class can also be subclassed if a custom variant of
* {@link EnableAutoConfiguration @EnableAutoConfiguration}. is needed.
*
* @deprecated as of 1.5 in favor of {@link AutoConfigurationImportSelector}
* @author Phillip Webb
* @author Andy Wilkinson
* @author Stephane Nicoll
* @author Madhura Bhave
* @since 1.3.0
* @see EnableAutoConfiguration
*/
@Deprecated
public class EnableAutoConfigurationImportSelector
extends AutoConfigurationImportSelector {
@Override
protected boolean isEnabled(AnnotationMetadata metadata) {if (getClass().equals(EnableAutoConfigurationImportSelector.class)) {
return getEnvironment().getProperty(
EnableAutoConfiguration.ENABLED_OVERRIDE_PROPERTY,
Boolean.class,
true);
}
return true;
}
}
上述源码有三处重点需要关注:
第一,EnableAutoConfigurationImportSelector是AutoConfigurationImportSelector的子类;
第二,EnableAutoConfigurationImportSelector已经被废弃了,不推荐使用;
第三,文档中已经写明废弃原因:从1.5版本开始,其特性由父类AutoConfigurationImportSelector实
现;
4. 查看AutoConfigurationImportSelector的源码,重点关注selectImports方法,该方法的返回值表
明了哪些类会被实例化:
@Override
public String[] selectImports(AnnotationMetadata annotationMetadata) {
if (!isEnabled(annotationMetadata)) {
return NO_IMPORTS;
}
try {
//将所有spring-autoconfigure-metadata.properties文件中的键值对保存在
autoConfigurationMetadata中
AutoConfigurationMetadata autoConfigurationMetadata =
AutoConfigurationMetadataLoader
.loadMetadata(this.beanClassLoader);
AnnotationAttributes attributes = getAttributes(annotationMetadata);
//取得所有配置类的名称
List<String> configurations =
getCandidateConfigurations(annotationMetadata,
attributes);
configurations = removeDuplicates(configurations);
configurations = sort(configurations, autoConfigurationMetadata);
Set<String> exclusions = getExclusions(annotationMetadata,
attributes);
checkExcludedClasses(configurations, exclusions);
configurations.removeAll(exclusions);
configurations = filter(configurations, autoConfigurationMetadata);
fireAutoConfigurationImportEvents(configurations, exclusions);
return configurations.toArray(new String[configurations.size()]);
}
catch (IOException ex) {
throw new IllegalStateException(ex);
}
}
5. 通过上述代码可以发现,getCandidateConfigurations方法的调用是个关键,它返回的字符串都是
即将被实例化的类名,来看此方法源码:protected List<String> getCandidateConfigurations(AnnotationMetadata metadata,
AnnotationAttributes attributes) {
List<String> configurations = SpringFactoriesLoader.loadFactoryNames(
getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader());
Assert.notEmpty(configurations,
"No auto configuration classes found in META
INF/spring.factories. If you "
+ "are using a custom packaging, make sure that file is
correct.");
return configurations;
}
6. getCandidateConfigurations方法中,调用了静态方法
SpringFactoriesLoader.loadFactoryNames,上面提到的
SpringFactoriesLoader.loadFactoryNames方法是关键,看看官方文档对此静态方法的描述,如
下图红框所示,该方法会在spring.factories文件中寻找指定接口对应的实现类的全名(包名+实现
类):
7. 在getCandidateConfigurations方法中,调用SpringFactoriesLoader.loadFactoryNames的时候
传入的指定类型是getSpringFactoriesLoaderFactoryClass方法的返回值:
protected Class<?> getSpringFactoriesLoaderFactoryClass() {
return EnableAutoConfiguration.class;
}
现在可以梳理一下了:
1. spring boot应用启动时使用了EnableAutoConfiguration注解;
2. EnableAutoConfiguration注解通过import注解将EnableAutoConfigurationImportSelector类实
例化,并且将其selectImports方法返回的类名实例化后注册到spring容器;
3. EnableAutoConfigurationImportSelector的selectImports方法返回的类名,来自spring.factories
文件内的配置信息,这些配置信息的key等于EnableAutoConfiguration;
现在真相大白了:只要我们在spring.factories文件内配置了EnableAutoConfiguration,那么对于的类
就会被实例化后注册到spring容器;
至此,《自定义spring boot starter三部曲》系列就完结了,希望实战加源码分析的三篇文章,能帮助
您理解和实现自定义starter这种简单快捷的扩展方式;