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

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.bootgroupId>
       <artifactId>spring-boot-starter-cacheartifactId>
   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.bootgroupId>
       <artifactId>mybatis-spring-boot-starterartifactId>
       <version>1.3.0version>
   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:

   version="1.0" encoding="UTF-8" ?>
   "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
   "com.example.demo.mapper.UserMapper" >
   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" />
   
   id="Base_Column_List" >
   id, nick_name, email_new, register_time
   
   id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Long" >
   select 
   "Base_Column_List" />
   from user
   where id = #{id,jdbcType=BIGINT}
   
   id="deleteByPrimaryKey" parameterType="java.lang.Long" >
   delete from user
   where id = #{id,jdbcType=BIGINT}
   
   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})
   
   id="insertSelective" parameterType="com.example.demo.model.User" >
   insert into user
   "(" 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>
   
   "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>
   
   
   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}
   
   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}
   
   

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/[email protected]

       http://127.0.0.1:8080/[email protected]

       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: "[email protected]",
           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: "[email protected]",
       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 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