config client踩坑记录--- Could not resolve placeholder* in value *

config client踩坑记录— Could not resolve placeholder* in value *

1.准备环境

​ eureka server: 注册中心

​ config server: 配置中心

​ config client: 配置客户端

2、开始踩坑

eureka server搭建不用说，很简单，引入netflix-eureka-server依赖就行了，然后配置注册中心，主程序加入注解就ok！

pom.xml

<dependencies>
    <dependency>
        <groupId>org.springframework.cloudgroupId>
        <artifactId>spring-cloud-starter-netflix-eureka-serverartifactId>
    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>

applicaiton.properties:

server.port= 8761
spring.application.name= eureka-server
eureka.client.service-url.default-zone = http://localhost:8761/eureka/
eureka.client.registry-fetch-interval-seconds=5000
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false

applcation主程序：

package top.juntech.springcloudeurekaserver;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer
public class SpringcloudEurekaServerApplication {

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

}

ok,eurekaserver就搭建好了，接下来我们搭建配置中心config-server

新建module ---->config-server—>引入config server依赖-------->配置文件-------》主程序加入注解

1、pom.xml

<properties>
        <java.version>1.8java.version>
        <spring-cloud.version>Greenwich.SR2spring-cloud.version>
    properties>
<dependencies>
    <dependency>
        <groupId>org.springframework.cloudgroupId>
        <artifactId>spring-cloud-config-serverartifactId>
    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>

2、application.yml(注释掉的部分是把配置中心文件放在git仓库的，为了方便，我们这里使用的是本地)

#server.port= 8763
#spring.application.name= config-server
#
##配置中心
#spring.cloud.config.server.git.uri= https://github.com/JunTech/springcloud-config-repo
#spring.cloud.config.server.git.password=
#spring.cloud.config.server.git.username=
#spring.cloud.config.server.git.search-paths=config-repo
#spring.cloud.config.label=master
server:
  port: 8763
spring:
  application:
    name: config-server
  profiles:
    active: native
  cloud:
    config:
      server:
        native:
          search-locations: classpath:/configRepo

3、在application.(*)文件当前目录下建立configRepo文件夹

search-locations: classpath:/configRepo 的意思是在configRepo文件夹下查找config client的配置文件

我们这里在文件夹configRepo中创建了一个文件：

config-client-dev.yml：

author: juntech
server:
  port: 10007

注意，我把端口信息放在配置中心的！

4、主程序加入注解，声明为配置中心

package top.juntech.springcloudconfigserver;

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

@SpringBootApplication
//加入注解声明为配置中心
@EnableConfigServer
public class SpringcloudConfigServerApplication {

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

}

ok,配置中心我们也弄完了！

最后，到config client环节了！！！！

激动否。。。

config client搭建

流程和上面的一毛一样。

新建module ---->config-client—>引入config client、eureka client依赖-------->配置文件-------》主程序加入注解

1、pom.xml引入依赖

<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>2.1.7.RELEASEversion>
        <relativePath/> 
    parent>
    <groupId>top.juntechgroupId>
    <artifactId>springcloud-config-clientartifactId>
    <version>0.0.1-SNAPSHOTversion>
    <name>springcloud-config-clientname>
    <description>Demo project for Spring Bootdescription>

    <properties>
        <java.version>1.8java.version>
        <spring-cloud.version>Greenwich.SR2spring-cloud.version>
    properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-netflix-eureka-clientartifactId>
            <version>2.0.2.RELEASEversion>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-configartifactId>
        dependency>

        <dependency>
            <groupId>org.projectlombokgroupId>
            <artifactId>lombokartifactId>
            <optional>trueoptional>
        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>

2、bootstrap.yml(注意，这里必须是bootstrap.yml,不然会报错)

spring:
  application:
    name: config-client
  profiles:
    active: dev
  cloud:
    config:
      uri: http://localhost:8763
eureka:
  client:
    service-url:
      default-zone: http://localhost:8761/eureka/

3、主程序

package top.juntech.springcloudconfigclient;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
@EnableDiscoveryClient
public class SpringcloudConfigClientApplication {

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

    @Value("${author}")
    private String author;

    @Value("${server.port}")
    private String port;

    @GetMapping("/hi")
    public String hi(){
        return "hi ,author : "+this.author+",i am from port : "+this.port;
    }
}

3、总结

上面的3个module按照eurekaserver—>config server---->config client依次运行，在打开localhost:8761

显示如下：

Instances currently registered with Eureka

Application	AMIs	Availability Zones	Status
CONFIG-CLIENT	n/a (1)	(1)	UP (1) - Ryan:config-client:10007

说明将config client注册到注册中心了，然后打开：http://localhost:10007/hi

hi ,author : juntech,i am from port : 10007

成功了。

总结如下：

​ 发生Could not resolve placeholder* in value *错误的可能原因有以下几种：

• ​ 配置中心profiles指定错误：

  spring:
    application:
      name: config-server
    profiles:
      active: native
  

  在这里，我每次都是写到spring.profiles就回车，显示就成了

  spring:
    application:
      name: config-server
    profiles: native  （x）
    这是错误的
  

• config client必须每个配置文件都必须以 bootstrap.yml命名

  之前我使用的是applicaiton.yml作为config client的配置文件，然后无一例外的都获取不到配置中心配置的server.port，每次运行都报错显示

  启动 config-client报错 Could not resolve placeholder 'server.port' in value "${server.port}"
  

若还不能解决你的问题，可重构项目，参考我上面的代码，进行配置中心的config client的搭建！

4、参考资料

• spring-cloud-config
• springcloud

更多详情

更多详情请访问： juntech