SpringBoot与Spring中数据缓存Cache超详细讲解

2022-11-13 19:11:16 数据缓存讲解

一、Spring缓存支持

Spring框架定义了org.springframework.cache CacheManager和org.springframework.cache.Cache接口来统一不同的缓存技术

CacheManager常用方法如下

1、@Cacheable

该注解可以标记在一个方法上，也可以标记在一个类上，当标记在一个方法上时表示该方法是支持缓存的，当标记在一个类上时则表示该类所有的方法都是支持缓存的。对于一个支持缓存的方法，在方法执行前，Spring先检查缓存中是否存在方法返回的数据，如果存在则直接返回缓存数据，如果不存在，则调用方法并将方法返回值存入缓存

2、@CacheEvict

该注解用来标注在需要清楚缓存元素的方法或类上，当标记在一个类上时，表示其中所有方法的执行都会触发缓存的清除操作

3、@CachePut

该注解也可以声明一个方法支持缓存功能

4、Caching

该注解可以在一个方法或类上同时指定多个Spring Cache相关的注解

5、CacheConfig

该注解作用在类上可以设置当前缓存的一些公共设置

二、Spring Boot缓存支持

1：创建基于spring-voot-starter-cache 和spring-boot-starter-data-jpa依赖的Spring BootWEB应用

2：配置application.properties文件代码如下

server.servlet.context-path=/ch6_10
###
##数据源信息配置
###
#数据库地址
spring.datasource.url=jdbc:Mysql://localhost:3306/SpringBootjpa?characterEncoding=utf8
#数据库用户名
spring.datasource.username=root
#数据库密码
spring.datasource.passWord=root
#数据库驱动
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
####
#JPA持久化配置
####
#指定数据库类型
spring.jpa.database=MYsql
#指定是否在日志中显示SQL语句
spring.jpa.show-sql=true
#指定自动创建、更新数据库表等配置，update表示如果数据库中存在持久化类对应的表就不创建，不存在就创建对应的表
spring.jpa.hibernate.ddl-auto=update
#让控制器输出的JSON字符串格式更美观
spring.jackson.serialization.indent-output=true

3：修改pom.xml文件添加mysql依赖

<?xml version="1.0" encoding="UTF-8"?>
-<project xsi:schemaLocation="Http://Maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0">
<modelVersion>4.0.0</modelVersion>
-<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.8.RELEASE</version>
<relativePath/>
<!-- lookup parent from repository -->
</parent>
<groupId>com.ch</groupId>
<artifactId>ch6_10</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>ch6_10</name>
<description>Demo project for Spring Boot</description>
-<properties>
<java.version>11</java.version>
</properties>
-<dependencies>
-<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-cache</artifactId>
</dependency>
-<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
-<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- 添加MySQL依赖 -->
-<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.45</version>
<!-- MySQL8.x时，请使用8.x的连接器 -->
</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>

4：创建持久化实体类

代码如下

package com.ch.ch6_10.entity;
import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import com.fasterxml.jackson.annotation.jsonIgnoreProperties;
@Entity
@Table(name = "student_table")
@JsonIgnoreProperties(value = {"hibernateLazyInitializer"})
public class Student implements Serializable{
	private static final long serialVersionUID = 1L;
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private int id;//主键
	private String sno;
	private String sname;
	private String ssex;
	public Student() {
		super();
	}
	public Student(int id, String sno, String sname, String ssex) {
		super();
		this.id = id;
		this.sno = sno;
		this.sname = sname;
		this.ssex = ssex;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getSno() {
		return sno;
	}
	public void setSno(String sno) {
		this.sno = sno;
	}
	public String getSname() {
		return sname;
	}
	public void setSname(String sname) {
		this.sname = sname;
	}
	public String getSsex() {
		return ssex;
	}
	public void setSsex(String ssex) {
		this.ssex = ssex;
	}  
}

5：创建数据访问接口

package com.ch.ch6_10.repository;
import org.springframework.data.jpa.repository.JpaRepository;
import com.ch.ch6_10.entity.Student;
public interface StudentRepository extends JpaRepository<Student, Integer>{
}

6：创建业务层包括一个接口和一个实现类

接口代码如下

package com.ch.ch6_10.service;
import com.ch.ch6_10.entity.Student;
public interface StudentService {
	public Student saveStudent(Student student);
	public void deleteCache(Student student);
	public Student selectOneStudent(Integer id);
}

实现类代码如下

package com.ch.ch6_10.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.CachePut;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;
import com.ch.ch6_10.entity.Student;
import com.ch.ch6_10.repository.StudentRepository;
@Service
public class StudentServiceImpl implements StudentService{
	@Autowired
	private StudentRepository studentRepository;
	@Override
	@CachePut(value = "student", key="#student.id")
	public Student saveStudent(Student student) {
		Student s = studentRepository.save(student);
		System.out.println("为key=" + student.getId() + "数据做了缓存");
		return s;
	}
	@Override
	@CacheEvict(value = "student", key="#student.id")
	public void deleteCache(Student student) {
		System.out.println("删除了key=" + student.getId() + "的数据缓存");
	}
	@Override
	@Cacheable(value = "student")
	public Student selectOneStudent(Integer id) {
		Student s = studentRepository.getOne(id);
		System.out.println("为key=" + id + "数据做了缓存");
		return s;
	}
}

7：创建控制器层

package com.ch.ch6_10.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.ch.ch6_10.entity.Student;
import com.ch.ch6_10.service.StudentService;
@RestController
public class TestCacheController {
	@Autowired
	private StudentService studentService;
	@RequestMapping("/savePut")
	public Student save(Student student) {
		return studentService.saveStudent(student);
	}
	@RequestMapping("/selectAble")
	public Student select(Integer id) {
		return studentService.selectOneStudent(id);
	}
	@RequestMapping("/deleteEvict")
	public String deleteCache(Student student) {
		studentService.deleteCache(student);
		return "ok";
	}
}

8：在主类中开启缓存支持

package com.ch.ch6_10;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;
@EnableCaching
@SpringBootApplication
public class Ch610Application {
	public static void main(String[] args) {
		SpringApplication.run(Ch610Application.class, args);
	}
}

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