JavaEE进阶知识学习----SpringBoot高级（二）SpringBoot使用缓存

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
1
@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

| 名字 | 描述 | 示例 |
| ———– | ———————————————————— | ——————– |
| methodName | 当前被调用的方法名 | #root.methodName |
| method | 当前被调用的方法 | #root.method.name |
| target | 当前被调用的目标对象 | #root.target |
| targetClass | 当前被调用的目标对象类 | #root.targetClass |
| args | 当前被调用的方法的参数列表 | #root.args[0] |
| caches | 当前方法调用使用的缓存列表（如@Cacheable(value={“cache1”,”cache2”})），则有两个cache | #root.caches[0].name |
| result | 方法执行后的返回值 | #result |
- CacheManager属性：指定缓存管理器
- condition:指定符合条件的才进入缓存
1
@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
1
2
// 使用unless判断结果为null就不缓存
@Cacheable(cacheNames = "emp",condition = "#id > 0",unless = "#result == null ")