springboot+cache緩存上

cache內容

緩存的意義：將方法的運行結果進行緩存，以後再要相同的數據，直接從緩存中獲取，不用調用方法；

cacheManager管理多個Cache組件，對緩存的真正操作CRUD操作在Cache組件中，每一個緩存組件有自己唯一一個名字；

幾個屬性：

• cacheNames/value:指定緩存的名字；

• key:緩存數據使用的key:可以用它來指定。默認是使用方法參數的值 1-方法的返回值
  編寫SpEL： #id:參數id的值 #a0 #p0 #root.args[0]

• keyGenerator: key的生成器；可以自己指定key的生成器的組件id

• cacheManager:指定緩存管理器；或者cacheResolver指定緩存解析器

• condition:指定符合條件的情況下緩存；condition = “#id>1"

• unless：否定緩存；當unless指定的條件爲true,方法的返回值就不會緩存，可以獲取到結果進行判斷; unless = “#result = null”

    @Cacheable(cacheNames = {"emp"},key="root.id")
    public Employee getEmpById(Integer id){
        System.out.println("查詢"+id+"號員工");
        Employee employee = employeeMapper.getEmpById(id);
        return employee;
    }

@CachePut:

//    @CachePut:既調用方法，又更新緩存數據；同步更新緩存
//    修改了數據庫的某個數據，同時更新緩存
//    運行：
//      1.先調用目標方法
//      2.將目標方法的結果緩存起來
    @CachePut(key= "#result.id")
    public Employee updateEmp(Employee employee){
        System.out.println("updateEmp"+employee);
        employeeMapper.updateEmpById(employee);
        return employee;
    }

@CacheEvict

//    @CacheEvict:緩存清除
//    key:指定要清除的數據
//    allEntries = true:指定清除這個緩存中的所有數據
//    beforeInvocation=true 代表清除緩存操作是在方法運行之前執行，無論方法是否出現異常，緩存都清除
    @CacheEvict
    public void deleteEmp(Integer id){
        System.out.println("deleteEmp:"+id);
        int i = 101/0;
        employeeMapper.deleteEmpById(id);
    }

搭建基本環境

1. 導入數據文件 創建出department和employee表
2. 創建Javabean封裝數據
3. 整合MyBatis操作數據庫 配置數據源信息

使用步驟

1. 導入模塊

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

2. 在主函數中開啓緩存模式 @EnableCaching

@EnableCaching
@SpringBootApplication
public class SpringbootCacheApplication {

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

}

3. 使用緩存註解

@CacheConfig(cacheNames = "emp")
@Service
public class EmployeeService {

    @Autowired
    EmployeeMapper employeeMapper;

    @Cacheable(cacheNames = {"emp"})
    public Employee getEmpById(Integer id){
        System.out.println("查詢"+id+"號員工");
        Employee employee = employeeMapper.getEmpById(id);
        return employee;
    }
    }

具體代碼

1.創建數據庫表

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;

2.創建bean文件

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 + "]";
	}

public class Employee {
	
	private Integer id;
	private String lastName;
	private String email;
	private Integer gender; //性別 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 + "]";
	}	
}

3.配置文件

spring.datasource.username=root
spring.datasource.password=root
spring.datasource.url=jdbc:mysql://localhost:3306/springcache?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=UTC
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

#開啓駝峯命名法
mybatis.configuration.map-underscore-to-camel-case=true

#打印sql語句日誌
logging.level.com.lxj.cache.mappers=debug

#控制檯打印配置信息
debug=true

4.創建mapper文件

package com.example.springbootcache.mappers;

import com.example.springbootcache.bean.Employee;
import org.apache.ibatis.annotations.*;

@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 updateEmpById(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 InsertEmp(Employee employee);

    @Select("SELECT * FROM employee WHERE lastName = #{lastName}")
    public Employee getEmpByLastName(String lastName);
}

5.創建service文件

@CacheConfig(cacheNames = "emp")
@Service
public class EmployeeService {

    @Autowired
    EmployeeMapper employeeMapper;

    @Cacheable(cacheNames = {"emp"})
    public Employee getEmpById(Integer id){
        System.out.println("查詢"+id+"號員工");
        Employee employee = employeeMapper.getEmpById(id);
        return employee;
    }

//    @CachePut:既調用方法，又更新緩存數據；同步更新緩存
//    修改了數據庫的某個數據，同時更新緩存
//    運行：
//      1.先調用目標方法
//      2.將目標方法的結果緩存起來
    @CachePut(key= "#result.id")
    public Employee updateEmp(Employee employee){
        System.out.println("updateEmp"+employee);
        employeeMapper.updateEmpById(employee);
        return employee;
    }

//    @CacheEvict:緩存清除
//    key:指定要清除的數據
//    allEntries = true:指定清除這個緩存中的所有數據
//    beforeInvocation=true 代表清除緩存操作是在方法運行之前執行，無論方法是否出現異常，緩存都清除

    public void deleteEmp(Integer id){
        System.out.println("deleteEmp:"+id);
        int i = 101/0;
        employeeMapper.deleteEmpById(id);
    }

}

6.創建controller文件

@RestController
public class EmployeeController {

    @Autowired
    EmployeeService employeeService;

    @GetMapping("/emp/{id}")
    public Employee getEmpById(@PathVariable("id") Integer id){
        Employee employee = employeeService.getEmpById(id);
        return  employee;
    }

    @GetMapping("/emp")
    public Employee updateEmp(Employee employee){
        Employee emp = employeeService.updateEmp(employee);
        return emp;
    }

    @GetMapping("/delEmp")
    public String deleteEmp(Integer id){
        employeeService.deleteEmp(id);
        return "success";
    }

}

工程的結構如下圖所示：

7.向數據庫添加測試數據

8.啓動服務，通過http://localhost:8080/emp/2查詢員工信息

以上說明這次查詢操作是通過查詢數據庫獲取的結果。

再次通過http://localhost:8080/emp/2查詢員工

這次沒有打印“查詢2號員工”，說明這次是從緩存查詢的數據。