不使用@PostConstruct或@AfterPropertiesSet的Spring引导缓存

Question

当我的应用程序启动时，我尝试用数据初始化我的缓存，但这不起作用。我的代码：

springBootApplication

package com.r2b.springcache;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.concurrent.ConcurrentMapCacheManager;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;

@ComponentScan("com.r2b")
@SpringBootApplication
@EnableCaching
public class SpringCacheApplication {

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

    @Bean
    public CacheManager cacheManager() {
        return new ConcurrentMapCacheManager("student");
    }
}

学生

package com.r2b.model;

public class Student {

    String id;
    String name;
    String clz;

    public Student(String id, String name, String clz) {
        super();
        this.id = id;
        this.name = name;
        this.clz = clz;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getClz() {
        return clz;
    }

    public void setClz(String clz) {
        this.clz = clz;
    }

    //Setters and getters

}

studentService

package com.r2b.service;

import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;

import com.r2b.model.Student;

@Service
public class StudentService  
{

    @Cacheable("student")
    public Student getStudentByID(String id)
    {
        try
        {
            System.out.println("Going to sleep for 5 Secs.. to simulate backend call.");
            Thread.sleep(1000*5);
        }
        catch (InterruptedException e)
        {
            e.printStackTrace();
        }

        return new Student(id,"Sajal" ,"V");
    }

}

StudentController

package com.r2b.controller;

import javax.annotation.PostConstruct;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import com.r2b.model.Student;
import com.r2b.service.StudentService;

@RestController
public class StudentController
{

    @Autowired
    StudentService studentService;


    @PostConstruct
    public void init() {
        studentService.getStudentByID("1");
    }

    @GetMapping("/student/{id}")
    public Student findStudentById(@PathVariable String id)
    {
        System.out.println("Searching by ID  : " + id);

        return studentService.getStudentByID(id);
    }
}

pom.xml

<?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>

    <groupId>com.r2b</groupId>
    <artifactId>spring-cache</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>spring-cache</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

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


</project>

当我第一次进入http://localhost:8080/student/1时，缓存是不活动的，响应需要超过5秒，但是当我刷新时，缓存会响应，请求需要几毫秒！尽管我在postConstruct中调用了缓存方法，但我尝试使用@AfterPropertiesSet，但它也不起作用！

知道吗？

谢谢

Answer 1

答案很简单，但我花了几乎一天的时间，才找到了在@PostConstruct中使用@Cacheable修饰的方法。

简单地将@PostConstruct替换为@EventListener(ApplicationReadyEvent.class)

@EventListener(ApplicationReadyEvent.class)
public void init() {
    studentService.getStudentByID("1");
}

如果从使用https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/context/event/EventListener.html(ApplicationReadyEvent.class) 事件修饰的方法引发异常，则应用程序将退出.

Answer 2

这不起作用，因为代理还没有初始化。这实际上是在用户指南中有记录

在代理模式(默认)中，只截获通过代理传入的外部方法调用。这意味着，即使被调用的方法标记为@Cacheable，自调用(实际上，在目标对象中调用另一个对象的方法)不会导致运行时的实际缓存。考虑在本例中使用aspectj模式。此外，代理必须完全初始化以提供预期的行为，因此您不应该在初始化代码(即@PostConstruct)中依赖此特性。

这正是你在这里要做的。缓存应该尽可能透明，所以在启动时预加载缓存对我来说有点奇怪(并且增加了启动时间)。