配置中心入门案例以及出现Could not resolve placeholder 'XXX' in value "${XXX}"的解决方式

编写配置中心的服务端
创建项目 修改 pom 文件添加 config-server 坐标

<?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>4.0.0modelVersion>
    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>2.1.11.RELEASEversion>
        <relativePath/> 
    parent>
    <groupId>com.bjsxtgroupId>
    <artifactId>config-serverartifactId>
    <version>0.0.1-SNAPSHOTversion>
    <name>config-servername>
    <description>config-serverdescription>

    <properties>
        <java.version>1.8java.version>
        <spring-cloud.version>Greenwich.SR4spring-cloud.version>
    properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-config-serverartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-netflix-eureka-clientartifactId>
        dependency>

        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>
        dependency>
    dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloudgroupId>
                <artifactId>spring-cloud-dependenciesartifactId>
                <version>${spring-cloud.version}version>
                <type>pomtype>
                <scope>importscope>
            dependency>
        dependencies>
    dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-maven-pluginartifactId>
            plugin>
        plugins>
    build>

project>

修改配置文件添加 Git 地址（将配置文件上传到gitee上）

spring.application.name=yxf-config-server
server.port=9010

eureka.client.service-url.defaultZone=http://admin:1234@192.168.41.242:5050/eureka/,http://admin:1234@192.168.41.242:5051/eureka/

#Git配置
spring.cloud.config.server.git.uri=https://gitee.com/sakurayxf/config
#spring.cloud.config.server.git.username=
#spring.cloud.config.server.git.password=

修改启动类

package com.bjsxt;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.config.server.EnableConfigServer;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication
@EnableEurekaClient
@EnableConfigServer
public class ConfigServerApplication {

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

}

创建四个临时配置文件

 注意命令规则

通过配置中心访问配置文件 编写配置中心的客户端 修改 pom 文件添加配置中心客户端坐标

<?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>4.0.0modelVersion>
    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>2.1.11.RELEASEversion>
        <relativePath/> 
    parent>
    <groupId>com.bjsxtgroupId>
    <artifactId>config-clientartifactId>
    <version>0.0.1-SNAPSHOTversion>
    <name>config-clientname>
    <description>config-clientdescription>

    <properties>
        <java.version>1.8java.version>
        <spring-cloud.version>Greenwich.SR4spring-cloud.version>
    properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-configartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-netflix-eureka-clientartifactId>
        dependency>

        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>
        dependency>
    dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloudgroupId>
                <artifactId>spring-cloud-dependenciesartifactId>
                <version>${spring-cloud.version}version>
                <type>pomtype>
                <scope>importscope>
            dependency>
        dependencies>
    dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-maven-pluginartifactId>
            plugin>
        plugins>
    build>

project>

修改启动类

package com.bjsxt;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.Bean;
import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;

@SpringBootApplication
@EnableEurekaClient
public class ConfigClientApplication {

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


}

修改配置文件 修改配置文件的名称。客户端配置文件名称必须为bootstrap.properties  

spring.application.name=config-client
server.port=9011

eureka.client.service-url.defaultZone=http://admin:1234@192.168.41.242:5050/eureka/,http://admin:1234@192.168.41.242:5051/eureka/

#默认 false,这里设置 true,表示开启读取配置中心的配置
spring.cloud.config.discovery.enabled=true
#对应 eureka 中的配置中心 serviceId，默认是 configserver
spring.cloud.config.discovery.service-id=yxf-config-server
#指定环境
spring.cloud.config.profile=dev
#git 标签
spring.cloud.config.label=master

编写测试代码

package com.bjsxt.controller;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ShowController {

    @Value("${e-book}")
    private String msg;

    @RequestMapping("/msg")
    public String Msg(){
        return msg;
    }

}

在写这个的过程中，实验了好几次都会出现这样的问题

 度娘也说了几种解决方法：

1.就是配置文件必须是bootstrap.properties/yml

2.就是

 去找注册中心中的服务必须名称正确。

3.就是我遇到的这种，

 客户端的名称必须是config-client，不会就读取不到值。

总之这个问题花费了我很长时间，最后还是老师过来帮我解决的，问题也是不容易发现。