Question

在我的应用程序启动时，我尝试使用数据初始化缓存，但无法正常工作。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，缓存未处于活动状态，并且响应花费了5秒钟以上，但是当我刷新时，缓存做出了响应，并且请求花费了几毫秒！尽管我在postConstruct中调用了缓存方法，但我尝试使用@AfterPropertiesSet，但它也无法正常工作！

有什么想法吗？

谢谢

Answer 1

这不起作用，因为尚未初始化代理。这实际上是documented in the user guide

在代理模式（默认）下，仅拦截通过代理传入的外部方法调用。这意味着即使调用的方法标记有@Cacheable，自调用（实际上是目标对象中的方法调用目标对象的另一种方法）也不会导致运行时实际缓存。在这种情况下，请考虑使用aspectj模式。另外，必须完全初始化代理以提供预期的行为，因此您不应在初始化代码（即@PostConstruct）中依赖此功能。

这正是您在这里所做的。缓存应尽可能透明，以便在启动时预加载缓存对我来说有点奇怪（并增加了启动时间）。

Answer 2

答案很简单，但是我花了 几乎一天 来找出用@Cacheable装饰的方法在@PostConstruct中没有任何作用

简单将您的@PostConstruct替换为@EventListener（ApplicationReadyEvent.class）

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

NB如果用@PostConstruct或EventListener（ApplicationReadyEvent.class）装饰的方法引发异常，则应用程序崩溃...

Spring Boot缓存不适用于@PostConstruct或@AfterPropertiesSet

2 个答案: