SpringBoot 手写 Starter-编程知识

spring-boot-starter 模块

1.介绍

SpringBoot中的starter是一种非常重要的机制，能够抛弃以前繁杂的配置，将其统一集成进starter，应用者只需要在maven中引入starter依赖，SpringBoot就能自动扫描到要加载的信息并启动相应的默认配置。starter让我们摆脱了各种依赖库的处理，需要配置各种信息的困扰。SpringBoot会自动通过classpath路径下的类发现需要的Bean，并注册进IOC容器。SpringBoot提供了针对日常企业应用研发各种场景的spring-boot-starter依赖模块。所有这些依赖模块都遵循着约定成俗的默认配置，并允许我们调整这些配置，即遵循“约定大于配置”的理念。

优点

一般认为，SpringBoot 微框架从两个主要层面影响 Spring 社区的开发者们：

基于 Spring 框架的“约定优先于配置（COC）”理念以及最佳实践之路。
提供了针对日常企业应用研发各种场景的 spring-boot-starter 自动配置依赖模块，如此多“开箱即用”的依赖模块，使得开发各种场景的 Spring 应用更加快速和高效。

SpringBoot 提供的这些“开箱即用”的依赖模块都约定以 spring-boot-starter- 作为命名的前缀，并且皆位于 org.springframework.boot 包或者命名空间下（虽然 SpringBoot 的官方参考文档中提到不建议大家使用 spring-boot-starter- 来命名自己写的类似的自动配置依赖模块，但实际上，配合不同的 groupId，这不应该是什么问题）。

2.starter自定义

springboot 官方建议springboot官方推出的starter 以spring-boot-starter-xxx的格式来命名，第三方开发者自定义的starter则以xxxx-spring-boot-starter的规则来命名，事实上，很多开发者在自定义starter的时候往往会忽略这个东西。

自定义一个分页：pagex-spring-boot-starter

开发步骤:

2.1新建工程

2.2父pom文件

<?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><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.3.11.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><packaging>pom</packaging><groupId>cn.jyx</groupId><artifactId>win-root</artifactId><version>1.0-SNAPSHOT</version><properties><java.version>8</java.version></properties><modules><module>win-model</module><module>win-core</module><module>pagex-spring-boot-starter</module><module>logtimex-spring-boot-starter</module></modules><dependencyManagement><dependencies><dependency><groupId>cn.hutool</groupId><artifactId>hutool-all</artifactId><version>5.8.16</version></dependency><dependency><groupId>com.github.pagehelper</groupId><artifactId>pagehelper-spring-boot-starter</artifactId><version>1.4.6</version></dependency></dependencies></dependencyManagement>
</project>

2.3model 模块

pom

<?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><parent><groupId>cn.jyx</groupId><artifactId>win-root</artifactId><version>1.0-SNAPSHOT</version><relativePath>../pom.xml</relativePath></parent><artifactId>win-model</artifactId><dependencies><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency></dependencies><build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-source-plugin</artifactId><executions><execution><id>attach-sources</id><phase>package</phase><goals><goal>jar</goal></goals></execution></executions></plugin></plugins></build>
</project>

响应返回对象

package cn.win.model;import lombok.Data;@Data
public class ResponseDTO {private int code;private String msg;private Object data;public static ResponseDTO success(Object data){ResponseDTO responseDTO = new ResponseDTO();responseDTO.setCode(0);responseDTO.setData(data);return responseDTO;}public static ResponseDTO error(int code,String msg){ResponseDTO responseDTO = new ResponseDTO();responseDTO.setCode(code);responseDTO.setMsg(msg);return responseDTO;}
}

2.4core模块

pom

<?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><parent><groupId>cn.jyx</groupId><artifactId>win-root</artifactId><version>1.0-SNAPSHOT</version><relativePath>../pom.xml</relativePath></parent><artifactId>win-core</artifactId><dependencies><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency></dependencies><build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-source-plugin</artifactId><executions><execution><id>attach-sources</id><phase>package</phase><goals><goal>jar</goal></goals></execution></executions></plugin></plugins></build></project>

声明调用注解

package cn.win.core.annotations;import java.lang.annotation.*;@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface PageX {
}

package cn.win.core.exceptioin;public class BizException extends RuntimeException {private int code;private String msg;public int getCode() {return code;}public BizException(int code, String msg) {super();this.code = code;this.msg = msg;}public void setCode(int code) {this.code = code;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}
}

pagex-spring-boot-starter 模块

<?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><parent><groupId>cn.jyx</groupId><artifactId>win-root</artifactId><version>1.0-SNAPSHOT</version><relativePath>../pom.xml</relativePath></parent><artifactId>pagex-spring-boot-starter</artifactId><dependencies><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>cn.hutool</groupId><artifactId>hutool-all</artifactId></dependency><dependency><groupId>com.github.pagehelper</groupId><artifactId>pagehelper-spring-boot-starter</artifactId></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId></dependency><dependency><groupId>org.aspectj</groupId><artifactId>aspectjweaver</artifactId></dependency><dependency><groupId>org.apache.tomcat.embed</groupId><artifactId>tomcat-embed-core</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-configuration-processor</artifactId><optional>true</optional></dependency><dependency><groupId>cn.jyx</groupId><artifactId>win-core</artifactId><version>1.0-SNAPSHOT</version><scope>compile</scope></dependency><dependency><groupId>cn.jyx</groupId><artifactId>win-model</artifactId><version>1.0-SNAPSHOT</version><scope>compile</scope></dependency></dependencies><build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-source-plugin</artifactId><executions><execution><id>attach-sources</id><phase>package</phase><goals><goal>jar</goal></goals></execution></executions></plugin></plugins></build></project>

全局响应处理类 advice

用于处理Spring MVC框架中的异常和响应体的转换

package cn.win.logtimex.advice;import cn.hutool.json.JSONUtil;
import cn.win.core.exceptioin.BizException;
import cn.win.model.ResponseDTO;
import com.github.pagehelper.Page;import org.springframework.core.MethodParameter;
import org.springframework.http.MediaType;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;import java.util.HashMap;@RestControllerAdvice
public class MyResponseAdvice implements ResponseBodyAdvice {@Overridepublic boolean supports(MethodParameter methodParameter, Class aClass) {return true;}@ExceptionHandler(Exception.class)public Object exceptionHandler(Exception ex){ex.printStackTrace();if(ex instanceof BizException){BizException bizException= (BizException) ex;return ResponseDTO.error(bizException.getCode(),bizException.getMsg());}return ResponseDTO.error(500, ex.getMessage());}@Overridepublic Object beforeBodyWrite(Object body, MethodParameter methodParameter, MediaType mediaType, Class aClass, ServerHttpRequest serverHttpRequest, ServerHttpResponse serverHttpResponse) {if (body instanceof ResponseDTO){return body;}ResponseDTO dto = ResponseDTO.success(body);if(body instanceof Page){Page page = (Page) body;long total = page.getTotal();HashMap<String,Object> map = new HashMap<>();map.put("total",total);map.put("items",body);dto = ResponseDTO.success(map);}if(aClass == StringHttpMessageConverter.class){return JSONUtil.toJsonStr(dto);}return dto;}
}

AOP

package cn.win.logtimex.aop;import cn.hutool.core.util.ObjectUtil;
import com.github.pagehelper.PageHelper;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;import javax.servlet.http.HttpServletRequest;@Component
@Aspect
public class PagexAop {//切点表达式，表示该切面将应用于所有被PageX注解标记的方法。@Pointcut("@annotation(cn.win.core.annotations.PageX)")public void point(){}@Around("point()")public Object around(ProceedingJoinPoint pjp) throws Throwable {System.out.println("执行方法之前");RequestAttributes requestAttributes= RequestContextHolder.getRequestAttributes();HttpServletRequest request = ((ServletRequestAttributes) requestAttributes).getRequest();String pageNum = request.getParameter("pageNum");String pageSize = request.getParameter("pageSize");if (ObjectUtil.isNotEmpty(pageNum)&&ObjectUtil.isNotEmpty(pageSize)){PageHelper.startPage(Integer.parseInt(pageNum),Integer.parseInt(pageSize));}Object result = pjp.proceed(); // 调用目标方法System.out.println("执行方法之后");return result;}
}

创建自动配置类AuthorityAutoConfigruation

package cn.win.logtimex.autoconfiguration;import cn.win.logtimex.advice.MyResponseAdvice;
import cn.win.logtimex.aop.PagexAop;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;@Configuration
@Import( {PagexAop.class, MyResponseAdvice.class})
// cn.smart.pagex.enbale = xxx
@ConditionalOnProperty(prefix = "cn.win.pagex", value = "enable",havingValue="true",matchIfMissing=true)
public class PageXAutoConfiguration { // 领头羊
}

配置类

package cn.win.logtimex.properties;import lombok.Data;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.context.properties.ConfigurationProperties;@Data
@ConfigurationProperties(prefix = "cn.win.pagex")
@EnableAutoConfiguration
public class PageXProperties {private boolean enable=true;
}

配置自动配置

在resourecs文件目录下创建META-INF，并创建我们自己的spring.factories，并把我们的 MemberStaterAutoConfiguration 添加进去

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\cn.win.logtimex.autoconfiguration.PageXAutoConfiguration