自定义一个springboot starter

作者: 御风_2fd9 | 来源:发表于2021-02-16 18:21 被阅读0次

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给提供的 Student/Klass/School 实现自动配置和 Starter。

一、自定义一个starter的实现方法

1.1 新建工程

xsj-spring-boot-starter

image.png

1.2 pom依赖

<?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 https://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>2.4.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.demo</groupId>
    <artifactId>xsj-spring-boot-starter</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>xsj-spring-boot-starter</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
    </dependencies>
</project>

1.3 定义一个实体类映射配置信息

@ConfigurationProperties(prefix = "student")，将“ student”前缀的配置映射成一个实体

package com.demo.properties;
import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties(prefix = "student")
@Data
public class StudentPropertise {
    private int id;
    private String name;
}

1.4 定义一个配置类

@EnableConfigurationProperties(StudentPropertise.class)，告诉springboot，支持步骤3.4中的ConfigurationProperties实体类映射配置。
@ConditionalOnProperty(
prefix = "student",
name = "isopen",
havingValue = "true"
)，控制@Configuration是否生效。
当配置前缀是student，含有isopen属性，且属性值为true时，@Configuration生效。

package com.demo.config;
import com.demo.properties.StudentPropertise;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Configuration;
@Configuration
@EnableConfigurationProperties(StudentPropertise.class)
@ConditionalOnProperty(
        prefix = "student",
        name = "isopen",
        havingValue = "true"
)
public class StudentConfig {
}

1.5 指定自动装配的配置类

image.png

spring.factories内容：

 org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
 com.demo.config.StudentConfig

1.6 生成starter

执行

mvn clean install

二、验证

2.1 在测试工程中引入pom依赖

<dependency>
            <groupId>com.demo</groupId>
            <artifactId>xsj-spring-boot-starter</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>

2.2 application.yml中配置依赖

student:
  id: 1
  name: xsj
  isopen: true

2.3 验证StudentPropertise类

package com.example.demo;

import com.demo.properties.StudentPropertise;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication implements CommandLineRunner {
    @Autowired
    private StudentPropertise studentPropertise;

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        System.out.println(studentPropertise);
    }
}

输出：

image.png

三、集合对象如何自动装配？

Klass是一个包含student集合的类。

3.1自定义实体映射配置信息

package com.demo.properties;
import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
import java.util.List;
@Data
@ConfigurationProperties(prefix = "klass")
public class KlassProperties {
    private List<StudentPropertise> students;
}

3.2 自定义配置类

ConditionalOnProperty注解非必须

package com.demo.config;
import com.demo.properties.KlassProperties;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Configuration;

@Configuration
@EnableConfigurationProperties(KlassProperties.class)
public class KlassConfig {
}

3.3 spring.factories中指定自动装配的配置类

 org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
 com.demo.config.StudentConfig,\
 com.demo.config.KlassConfig

3.4 如何配置

在测试工程的yml文件中增加以下配置，springboot会将这些配置自动装配成一个KlassProperties实体

klass:
  students:
    - id: 11
      name: xu
    - id: 12
      name: sj

四、踩坑

4.1.自定义的starter工程中不可添加启动入口类，否则，install之后无法引入starter中的类。

4.2 自定的starter工程中把启动入口类去掉，还要把maven插件去掉，不然install时会保存，这个插件会自动去找启动入口类，如果找不到，install会失败。

<build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>