Spring Boot设置并使用缓存的步骤

几个缓存注解的作用：

@Cacheable：将方法的返回结果根据key指定的键保存在缓存中，以后要获取相同的数据直接从缓存中共获取

• cacheNames/value：指定Cache组件名称
• key：指定缓存时使用的key，默认使用方法参数值，可以使用#a0、#p0、#参数名等，支持SpEL表达式，root可省略
• keyGenerator：指定key的生成器的组件id，如自定义的KeyGenerator
• cacheManager：指定缓存管理器
• cacheResolver：指定缓存解析器
• condition：指定在哪种条件下缓存，如condition = “#id>=1”在参数>=1时缓存
• unless：指定该条件为真时不缓存
• sync：指定是否使用异步模式

@CachePut：不管缓存中是否有需要的数据，都会执行该注解标注的方法，并将结果更新到缓存，属性见上

@CacheEvit：执行方法后，清除key指定的缓存

• allEntries：默认为false，值为true，删除所有缓存
• beforeInvocation：默认为false，值为true，在方法调用之前清除缓存

@CacheConfig：定义一些通用或公共的规则，如cacheNames、keyGenerator等

可使用的SpEL表达式：

使用缓存的步骤：

（1）创建一个Spring Boot应用，勾选Cache、Web、MySQL、Mybatis模块,在主程序类上添加注解，开启基于注解的缓存

@MapperScan(basePackages = "com.youngpain.cache.mapper")
@SpringBootApplication
@EnableCaching

（2）创建JavaBean，和数据库中的表对应，并配置数据源

spring:
 datasource:
  url: jdbc:mysql://localhost:3306/mybatis_database
  username: root
  password: 1741248769
  driver-class-name: com.mysql.jdbc.Driver
 redis:
  host: 39.108.114.57
#开启驼峰命名法
mybatis:
 configuration:
  map-underscore-to-camel-case: true
logging:
 level:
  com.youngpain.cache.mapper: debug

（3）创建mapper接口进行增删改查操作

/**
 * 部门表的增删改查操作
 */
public interface DepartmentMapper {
  @Insert("insert into department(id,depart_name,depart_build) values(#{id},#{depart_name},#{depart_build})")
  void insertDepartment(Department department);
  @Delete("delete from department where id=#{id}")
  void deleteDepartment(Integer id);
  @Update("update department set depart_name=#{departName},depart_build=#{departBuild} where id=#{id}")
  void updateDepartment(Department department);
  @Select("select * from department where id=#{id}")
  Department getDepartmentById(Integer id);
}

（4）创建service

@Service
@CacheConfig(cacheNames = {"departs"})
public class DepartmentService {
  @Autowired
  DepartmentMapper departmentMapper;
  @Cacheable(key = "#a0.id")
  public void insertDepartment(Department department) {
    departmentMapper.insertDepartment(department);
  }
  @CacheEvict(key = "#p0")
  public void deleteDepartment(Integer id) {
    departmentMapper.deleteDepartment(id);
  }
  @CachePut(key = "#a0.id")
  public Department updateDepartment(Department department) {
    departmentMapper.updateDepartment(department);
    return department;
  }
  @Cacheable(key = "#id", condition = "#p0>=1")
  public Department getDepartmentById(Integer id) {
    return departmentMapper.getDepartmentById(id);
  }
}

（5）创建controller

@Controller
public class DepartmentController {
  @Autowired
  DepartmentService departmentService;
  @GetMapping("/index")
  public String index() {
    return "index";
  }
  @GetMapping("/deleteDepart/{id}")
  public String deleteDepart(@PathVariable("id") Integer id, Model model) {
    model.addAttribute("condition", "delete");
    Department delete = departmentService.getDepartmentById(id);
    model.addAttribute("department", delete);
    departmentService.deleteDepartment(id);
    return "success";
  }
  @PostMapping("/updateDepart")
  public String updateDepart(Department department, Model model) {
    model.addAttribute("condition", "update");
    Department update = departmentService.updateDepartment(department);
    model.addAttribute("department", update);
    return "success";
  }
  @GetMapping("/getDepart/{id}")
  public String getDepartmentById(@PathVariable("id") Integer id, Model model) {
    model.addAttribute("condition", "delete");
    Department get = departmentService.getDepartmentById(id);
    model.addAttribute("department", get);
    return "success";
  }
}

（6）测试结果：

@Cacheable：第一次查询数据，控制台发出sql语句，之后再查询直接从缓存中获取
@CachePut：调用方法修改某个数据后，再次查询该数据是从缓存中获取的更新后的数据
@CacheEvict：调用该方法后，再次查询某个数据需要重新发出sql语句查询

ps：之前只是用markdown记笔记，今天第一次用markdown写文章，写起来好舒服啊QAQ

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