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缓存使用

1.使用IDEA创建SpringBoot项目，引入cache模块，web模块，mysql模块，Mybatis模块

2.创建mysql数据库spring_cache

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------
-- Table structure for department
-- ----------------------------
DROP TABLE IF EXISTS `department`;
CREATE TABLE `department` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `departmentName` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------
-- Table structure for employee
-- ----------------------------
DROP TABLE IF EXISTS `employee`;
CREATE TABLE `employee` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `lastName` varchar(255) DEFAULT NULL,
  `email` varchar(255) DEFAULT NULL,
  `gender` int(2) DEFAULT NULL,
  `d_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

3.创建JavaBean封装数据

package com.springboot.cache.bean;

public class Employee {
    private Integer id;
    private String lastName;
    private String email;
    private Integer gender; //性别 1男  0女
    private Integer dId;
    public Employee() {
        super();
    }
    public Employee(Integer id, String lastName, String email, Integer gender, Integer dId) {
        super();
        this.id = id;
        this.lastName = lastName;
        this.email = email;
        this.gender = gender;
        this.dId = dId;
    }
    public Integer getId() {

        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    public Integer getGender() {
        return gender;
    }
    public void setGender(Integer gender) {
        this.gender = gender;
    }
    public Integer getdId() {
        return dId;
    }
    public void setdId(Integer dId) {
        this.dId = dId;
    }
    @Override
    public String toString() {
        return "Employee [id=" + id + ", lastName=" + lastName + ", email=" + email + ", gender=" + gender + ", dId="
                + dId + "]";
    }
}

package com.springboot.cache.bean;

public class Department {
    private Integer id;
    private String departmentName;
    public Department() {
        super();
        // TODO Auto-generated constructor stub
    }
    public Department(Integer id, String departmentName) {
        super();
        this.id = id;
        this.departmentName = departmentName;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getDepartmentName() {

        return departmentName;
    }
    public void setDepartmentName(String departmentName) {
        this.departmentName = departmentName;
    }
    @Override
    public String toString() {
        return "Department [id=" + id + ", departmentName=" + departmentName + "]";
    }
}

4.整合Mybatis

• Application.properties中配置数据源

spring.datasource.url=jdbc:mysql://localhost:3306/spring_cache
spring.datasource.username=root
spring.datasource.password=1234
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

mybatis.configuration.map-underscore-to-camel-case=true
logging.level.com.springboot.cache.mapper = debug

• 使用注解版的Mybatis

  • 使用@MapperScan指定需要扫描的Mapper接口所在的包

  @MapperScan("com.springboot.cache.mapper")
  @SpringBootApplication
  public class CacheApplication {
  public static void main(String[] args) {
      SpringApplication.run(CacheApplication.class, args);
  }
  }

  • 编写Employee接口和DepartmentMapper接口

  @Mapper
  public interface EmployeeMapper {
  
    @Select("select * from employee where id = #{id}")
    public  Employee getEmpById(Integer id);
  
    @Update("update employee set lastName = #{lastName},email = #{email},gender = #{gender},d_id = #{did} where id = #{id}")
    public void updateEmp(Employee employee);
  
    @Delete("delete from employee where id = #{id}")
    public void deleteEmpById(Integer id);
  
    @Insert("insert into employee(lastName.email,gender,d_id) values(#{lastName},#{email},#{gender},#{did})")
    public void insertEmployee(Employee employee);
  }

  • 
    编写service层代码
    

  @Service
  public class EmployeeService {
  
    @Autowired
    private EmployeeMapper employeeMapper;
  
    public Employee getEmp(Integer id){
        return employeeMapper.getEmpById(id);
    }
  }

  • 
    编写controller层代码
    

  @RestController
  public class EmployeeController {
  
    @Autowired
    private EmployeeService employeeService;
  
    @GetMapping("/emp/{id}")
    public Employee getEmployee(@PathVariable("id") Integer id){
        Employee emp = employeeService.getEmp(id);
        return emp;
    }
  }

5.开启基于注解@EnableCaching的缓存

@MapperScan("com.springboot.cache.mapper")
@SpringBootApplication
@EnableCaching
public class CacheApplication {

    public static void main(String[] args) {
        SpringApplication.run(CacheApplication.class, args);
    }
}

6.标注缓存注解即可

@Service
public class EmployeeService {

    @Autowired
    private EmployeeMapper employeeMapper;

    /**
     * 将方法结果进行缓存，以后再要相同的数据，就直接从缓存中去
     * @param id
     * @return
     */
    @Cacheable(cacheNames = "emp" , key = "#id")
    public Employee getEmp(Integer id){
        return employeeMapper.getEmpById(id);
    }
}

注解@Cacheable说明：

• 将方法结果进行缓存，以后再要相同的数据，就直接从缓存中去

• 属性说明：

  • cacheNames/value:指定缓存组件的名字，CacheManager管理多个cache组件，对缓存的真正CRUD操作在Cache中，每一个缓存都有自己唯一的一个名字
  • key:缓存数据使用的key,可以使用这个属性来指定，默认是使用方法参数的值1，方法的返回值

  @Cacheable(cacheNames = "emp" , key = "#id")

  缓存的名字是emp，key是方法中参数id的值，这种写法还有如下可以取到其他参数

– CacheManager属性：指定缓存管理器

– condition:指定符合条件的才进入缓存


java

@Cacheable(cacheNames = "emp",condition = "#id > 0")



• unless：否定缓存，当unless指定的条件为true,该方法的返回值就不会被缓存，可以获取结果进行判断

  // 使用unless判断结果为null就不缓存
  @Cacheable(cacheNames = "emp",condition = "#id > 0",unless = "#result == null ")