Spring Boot 配置随机值

为什么我们需要配置随机值？例如，我们想让我们的应用每次启动均使用不同的端口，然后自动打开浏览器访问该应用，这样将避免由于端口冲突导致应用启动失败。Spring Boot 支持在配置文件中生成随机整数、随机字符串和 UUID，并且随机整数允许控制在指定的范围之内。下面将详解介绍 Spring Boot 配置文件对随机值的支持。

应用依赖

该 Spring Boot 的 pom.xml 依赖如下：

<?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 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>2.7.13</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.hxstrive</groupId>
    <artifactId>springboot2_demos_demo01</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot2_demos_demo01</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>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-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
            <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>

</project>

springboot广告位

应用配置

修改 application.yml 配置文件，内容如下：

hxstrive:
  # 随机整数
  value1: ${random.int}
  # 10以内的随机数
  value2: ${random.int(10)}
  # 10到20之间的随机数
  value3: ${random.int(10,20)}
  # 随机字符串，MD5字符串，32位
  value4: ${random.value}
  # 随机UUID
  value5: ${random.uuid}
  # 随机整数（范围 long）
  value6: ${random.long}
  # 随机整数（范围：10~100）
  value7: ${random.long(10, 100)}

Java代码

package com.hxstrive.springboot2_demos_demo01;

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

import java.util.Date;

@RestController
@SpringBootApplication
public class Springboot2DemosDemo01Application {

    // 注入值
    @Value("${hxstrive.value1}")
    private String value1;

    @Value("${hxstrive.value2}")
    private String value2;

    @Value("${hxstrive.value3}")
    private String value3;

    @Value("${hxstrive.value4}")
    private String value4;

    @Value("${hxstrive.value5}")
    private String value5;

    @Value("${hxstrive.value6}")
    private String value6;

    public static void main(String[] args) {
        SpringApplication.run(Springboot2DemosDemo01Application.class, args);
    }

    @GetMapping("/")
    public String index() {
        System.out.println("value1=" + value1);
        System.out.println("value2=" + value2);
        System.out.println("value3=" + value3);
        System.out.println("value4=" + value4);
        System.out.println("value5=" + value5);
        System.out.println("value6=" + value6);
        return new Date().toString();
    }


}

运行应用，使用浏览器访问 http://localhost:8080，控制台输出如下：

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::               (v2.7.13)

...
2023-07-22 10:36:59.718  INFO 1292 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : Completed initialization in 2 ms
value1=-885549549
value2=8
value3=16
value4=8256b006362bf893139358f4f0e06223
value5=bc930440-002f-479d-9302-c44348acf13c
value6=-6320840787392360533