spring boot 源码解析33-spring boot集成spring cache(基于ConcurrentMapCache)

2023年3月7日 347次阅读 来源: Spring Boot

前言

接下来的几篇我们来讲解一下spring boot 中如何集成spring cache. spring cache 中支持如下cache:

  1. ConcurrentMap Cache
  2. Caffeine Cache
  3. EhCache
  4. GuavaCache(1.5版本废弃)
  5. Hazelcast Cache
  6. Infinispan Cache
  7. JCache Cache

我们只讲解ConcurrentMapCache和EhCache,其他的cache感兴趣的可以查阅相关资料.本文首先来看下ConcurrentMapCache.

ConcurrentMapCache集成

  1. 在pom文件中加入如下依赖:

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

  2. 在启动类加上@EnableCaching注解开始spring cache的支持.

  3. 由于加入cache,为了模拟的方便,我们加入mybatis,pom文件加入如下配置:

    <dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.3.0</version>
</dependency>

    在application.properties中加入如下配置:

    mybatis.mapper-locations=classpath:com/example/demo/mapper/*.xml

    在启动类中加入如下注解即可:

    @MapperScan("com.example.demo.mapper")

  4. UserMapper如下:

    package com.example.demo.mapper;

import com.example.demo.model.User;

public interface UserMapper {
    int deleteByPrimaryKey(Long id);

    int insert(User record);

    int insertSelective(User record);

    User selectByPrimaryKey(Long id);

    int updateByPrimaryKeySelective(User record);

    int updateByPrimaryKey(User record);
}

  5. User,代码如下:

    package com.example.demo.model;
import java.util.Date;
public class User {
    private Long id;

    private String nickName;

    private String emailNew;

    private Date registerTime;

    public Long getId() {
        return id;
    }

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

    public String getNickName() {
        return nickName;
    }

    public void setNickName(String nickName) {
        this.nickName = nickName == null ? null : nickName.trim();
    }

    public String getEmailNew() {
        return emailNew;
    }

    public void setEmailNew(String emailNew) {
        this.emailNew = emailNew == null ? null : emailNew.trim();
    }

    public Date getRegisterTime() {
        return registerTime;
    }

    public void setRegisterTime(Date registerTime) {
        this.registerTime = registerTime;
    }
}

  6. UserMapper.xml 如下:

    <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.example.demo.mapper.UserMapper" >
<resultMap id="BaseResultMap" type="com.example.demo.model.User" >
<id column="id" property="id" jdbcType="BIGINT" />
<result column="nick_name" property="nickName" jdbcType="VARCHAR" />
<result column="email_new" property="emailNew" jdbcType="VARCHAR" />
<result column="register_time" property="registerTime" jdbcType="TIMESTAMP" />
</resultMap>
<sql id="Base_Column_List" >
id, nick_name, email_new, register_time
</sql>
<select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Long" >
select 
<include refid="Base_Column_List" />
from user
where id = #{id,jdbcType=BIGINT}
</select>
<delete id="deleteByPrimaryKey" parameterType="java.lang.Long" >
delete from user
where id = #{id,jdbcType=BIGINT}
</delete>
<insert id="insert" parameterType="com.example.demo.model.User" >
insert into user (id, nick_name, email_new, 
  register_time)
values (#{id,jdbcType=BIGINT}, #{nickName,jdbcType=VARCHAR}, #{emailNew,jdbcType=VARCHAR}, 
  #{registerTime,jdbcType=TIMESTAMP})
</insert>
<insert id="insertSelective" parameterType="com.example.demo.model.User" >
insert into user
<trim prefix="(" suffix=")" suffixOverrides="," >
  <if test="id != null" >
    id,
  </if>
  <if test="nickName != null" >
    nick_name,
  </if>
  <if test="emailNew != null" >
    email_new,
  </if>
  <if test="registerTime != null" >
    register_time,
  </if>
</trim>
<trim prefix="values (" suffix=")" suffixOverrides="," >
  <if test="id != null" >
    #{id,jdbcType=BIGINT},
  </if>
  <if test="nickName != null" >
    #{nickName,jdbcType=VARCHAR},
  </if>
  <if test="emailNew != null" >
    #{emailNew,jdbcType=VARCHAR},
  </if>
  <if test="registerTime != null" >
    #{registerTime,jdbcType=TIMESTAMP},
  </if>
</trim>
</insert>
<update id="updateByPrimaryKeySelective" parameterType="com.example.demo.model.User" >
update user
<set >
  <if test="nickName != null" >
    nick_name = #{nickName,jdbcType=VARCHAR},
  </if>
  <if test="emailNew != null" >
    email_new = #{emailNew,jdbcType=VARCHAR},
  </if>
  <if test="registerTime != null" >
    register_time = #{registerTime,jdbcType=TIMESTAMP},
  </if>
</set>
where id = #{id,jdbcType=BIGINT}
</update>
<update id="updateByPrimaryKey" parameterType="com.example.demo.model.User" >
update user
set nick_name = #{nickName,jdbcType=VARCHAR},
  email_new = #{emailNew,jdbcType=VARCHAR},
  register_time = #{registerTime,jdbcType=TIMESTAMP}
where id = #{id,jdbcType=BIGINT}
</update>
</mapper>

  7. UserService如下:

    package com.example.demo.service;

import com.example.demo.model.User;

public interface UserService {

    int insertSelective(User record);

    User selectByPrimaryKey(Long id);

    User updateByPrimaryKeySelective(User record);

    int deleteByPrimaryKey(Long id);
}

  8. UserServiceImpl 如下:

    package com.example.demo.service;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
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.example.demo.mapper.UserMapper;
import com.example.demo.model.User;
@Service
public class UserServiceImpl implements UserService{

    private static Logger logger = LoggerFactory.getLogger(UserServiceImpl.class);

    @Autowired
    private UserMapper userMapper;

    @Override
    public int insertSelective(User record) {
        return userMapper.insertSelective(record);
    }

    @Override
    @Cacheable(cacheNames="users",key="#id")
    public User selectByPrimaryKey(Long id) {
        logger.info("查询数据库");
        return userMapper.selectByPrimaryKey(id);
    }

    @Override
    @CachePut(cacheNames="users",key="#record.id")
    public User updateByPrimaryKeySelective(User record) {
        userMapper.updateByPrimaryKeySelective(record);
        return userMapper.selectByPrimaryKey(record.getId());
    }

    @Override
    @CacheEvict(cacheNames="users",key="#id")
    public int deleteByPrimaryKey(Long id) {
        return userMapper.deleteByPrimaryKey(id);
    }
}

    这里有必要说明一下spring cache相关的注解:

    • @CacheConfig：主要用于配置该类中会用到的一些共用的缓存配置

    • @Cacheable：配置了findByName函数的返回值将被加入缓存。同时在查询时，会先从缓存中获取，若不存在才再发起对数据库的访问。该注解主要有下面几个参数：

      • value、cacheNames：两个等同的参数（cacheNames为Spring 4新增，作为value的别名），用于指定缓存存储的集合名。由于Spring 4中新增了@CacheConfig，因此在Spring 3中原本必须有的value属性，也成为非必需项了

      • key：缓存对象存储在Map集合中的key值，非必需，缺省按照函数的所有参数组合作为key值，若自己配置需使用SpEL表达式，比如：@Cacheable(key = “#p0”)：使用函数第一个参数作为缓存的key值

      • condition：缓存对象的条件，非必需，也需使用SpEL表达式，只有满足表达式条件的内容才会被缓存，比如：@Cacheable(key = “#p0”, condition = “#p0.length() < 3”)，表示只有当第一个参数的长度小于3的时候才会被缓存
      • unless：另外一个缓存条件参数，非必需，需使用SpEL表达式。它不同于condition参数的地方在于它的判断时机，该条件是在函数被调用之后才做判断的，所以它可以通过对result进行判断。
      • keyGenerator：用于指定key生成器，非必需。若需要指定一个自定义的key生成器，我们需要去实现org.springframework.cache.interceptor.KeyGenerator接口，并使用该参数来指定。需要注意的是：该参数与key是互斥的
      • cacheManager：用于指定使用哪个缓存管理器，非必需。只有当有多个时才需要使用
      • cacheResolver：用于指定使用那个缓存解析器，非必需。需通过org.springframework.cache.interceptor.CacheResolver接口来实现自己的缓存解析器，并用该参数指定。

    • @CachePut：配置于函数上，能够根据参数定义条件来进行缓存，它与@Cacheable不同的是，它每次都会真是调用函数，所以主要用于数据新增和修改操作上。它的参数与@Cacheable类似，具体功能可参考上面对@Cacheable参数的解析

    • @CacheEvict：配置于函数上，通常用在删除方法上，用来从缓存中移除相应数据。除了同@Cacheable一样的参数之外，它还有下面两个参数：
      • allEntries：非必需，默认为false。当为true时，会移除所有数据
      • beforeInvocation：非必需，默认为false，会在调用方法之后移除数据。当为true时，会在调用方法之前移除数据。

    参考链接如下:

    Spring Boot中的缓存支持（一）注解配置与EhCache使用

    Spring4.1新特性——Spring缓存框架增强

  9. UserController,代码如下:

    package com.example.demo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import com.example.demo.model.User;
import com.example.demo.service.UserService;
@Controller
public class UserController {

    @Autowired
    private UserService userService;

    @RequestMapping("/add-user")
    @ResponseBody
    public String insertSelective(User record) {
        userService.insertSelective(record);
        return "OK";
    }

    @RequestMapping("/get-by-id")
    @ResponseBody
    public User selectByPrimaryKey(Long id) {
        return userService.selectByPrimaryKey(id);
    }

    @RequestMapping("/update-by-id")
    @ResponseBody
    public String update(User record) {
        userService.updateByPrimaryKeySelective(record);
        return "ok";
    }

    @RequestMapping("/delete-by-id")
    @ResponseBody
    public Integer delete(Long id) {
        return userService.deleteByPrimaryKey(id);
    }  
}

  10. 测试:

    1. 首先我们访问如下链接:

      http://127.0.0.1:8080/add-user?nickName=harry&emailNew=xxx@xxx.com

      http://127.0.0.1:8080/add-user?nickName=harry2&emailNew=xxx@xxx.com

      加入2条数据

    2. 然后我们访问如下链接:

      http://127.0.0.1:8080/get-by-id?id=1

      发现有打印日志,如下:

      2018-01-23 14:52:41.658  INFO 60766 --- [nio-8881-exec-6] c.example.demo.service.UserServiceImpl   : 查询数据库

      返回值如下:

      { id: 1, nickName: "harry", emailNew: "xxx@xxx.com", registerTime: 1484488802000 }

      此时我们再次访问,发现没有再次打印日志,而是直接从缓存中返回的.

    3. 访问如下链接就行修改:

      http://127.0.0.1:8080/update-by-id?id=1&nickName=22

      将昵称改为22.

      此时我们继续访问 http://127.0.0.1:8080/get-by-id?id=1 ,发现没有打印日志,且返回的结果中昵称也改为了22,如下:

      {
id: 1,
nickName: "22",
emailNew: "xxx@xxx.com",
registerTime: 1484488802000
}

ConcurrentMapCache解析

ConcurrentMapCache的自动装配声明在SimpleCacheConfiguration中.

  1. SimpleCacheConfiguration 声明了如下注解:

    @Configuration
@ConditionalOnMissingBean(CacheManager.class)
@Conditional(CacheCondition.class)
    • @Configuration –> 配置类
    • @ConditionalOnMissingBean(CacheManager.class)–> 当BeanFactory中缺少CacheManager类型的bean时生效

    • @Conditional(CacheCondition.class) –> 通过CacheCondition来进行判断,代码如下:

      public ConditionOutcome getMatchOutcome(ConditionContext context,
    AnnotatedTypeMetadata metadata) {
    // 1. 获得被注解的类名
    String sourceClass = "";
    if (metadata instanceof ClassMetadata) {
        sourceClass = ((ClassMetadata) metadata).getClassName();
    }
    ConditionMessage.Builder message = ConditionMessage.forCondition("Cache",
            sourceClass);
    // 2. 实例化RelaxedPropertyResolver,读取spring.cache.开头的属性
    RelaxedPropertyResolver resolver = new RelaxedPropertyResolver(
            context.getEnvironment(), "spring.cache.");
    // 3. 如果没有配置spring.cache.type,则返回匹配--> 进行自动选择
    if (!resolver.containsProperty("type")) {
        return ConditionOutcome.match(message.because("automatic cache type"));
    }
    // 4. 根据被注解的类名获得对应的CacheType
    CacheType cacheType = CacheConfigurations
            .getType(((AnnotationMetadata) metadata).getClassName());
    // 5. 将spring.cache.type 配置的值 中的-变为_,然后变成大写,如果和CacheType的name相等的化,则返回匹配,否则,返回不匹配
    String value = resolver.getProperty("type").replace('-', '_').toUpperCase();
    if (value.equals(cacheType.name())) {
        return ConditionOutcome.match(message.because(value + " cache type"));
    }
    return ConditionOutcome.noMatch(message.because(value + " cache type"));
}
      1. 获得被注解的类名,对于当前是org.springframework.boot.autoconfigure.cache.SimpleCacheConfiguration
      2. 实例化RelaxedPropertyResolver,读取spring.cache.开头的属性
      3. 如果没有配置spring.cache.type,则返回匹配–> 进行自动选择. 由于默认情况下是没有配置spring.cache.type的,因此,在这里返回.
      4. 根据被注解的类名获得对应的CacheType
      5. 将spring.cache.type 配置的值 中的-变为_,然后变成大写,如果和CacheType的name相等的化,则返回匹配,否则,返回不匹配

  2. bean方法,代码如下:

    @Bean
public ConcurrentMapCacheManager cacheManager() {
    ConcurrentMapCacheManager cacheManager = new ConcurrentMapCacheManager();
    List<String> cacheNames = this.cacheProperties.getCacheNames();
    if (!cacheNames.isEmpty()) {
        cacheManager.setCacheNames(cacheNames);
    }
    return this.customizerInvoker.customize(cacheManager);
}
    • @Bean –> 注册1个id为cacheManager,类型为ConcurrentMapCacheManager的bean

    该方法的处理逻辑如下:

    1. 实例化ConcurrentMapCacheManager
    2. 如果配置有spring.cache.cache-names=xx,xx,则进行配置cacheNames,默认是没有配置的
    3. 调用CacheManagerCustomizers#customize 进行个性化设置,在该方法中是遍历其持有的List
    原文作者：Spring Boot
    原文地址: https://blog.csdn.net/qq_26000415/article/details/79140427
    本文转自网络文章，转载此文章仅为分享知识，如有侵权，请联系博主进行删除。
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