一、简介
在hibernate中就是用到了ehcache 充当缓存。spring对ehcache也提供了支持，使用也比较简单，只需在spring的配置文件中将ehcache的ehcache.xml文件配置进去即可。在spring中使用ehcache有两种方式，一种是使用spring提供的封装，使用注解的方式配置在某个方法上面，第一次调用该方法的时候，将该方法执行返回的数据缓存，当再次执行的时候如果时间没有变，就直接冲缓存获取，该方法不执行；另一种方式是获取到ehcache本地接口，直接使用ehcache本地接口进行数据缓存。第一种的方式使用简单，代码简洁，但灵活度不高，而第二种方式灵活度高，但是代码就比较到，需要自己去判断数据是否缓存，如何没有缓存就去获取上海并本放入缓；如果缓存了，就直接去缓存中获取。本例子是用的是第一种方式。
工程使用maven构建，需要的依赖如下：
<dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>3.2.6.RELEASE</version> </dependency> <dependency> <groupId>net.sf.ehcache</groupId> <artifactId>ehcache-core</artifactId> <version>2.4.2</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>3.2.6.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context-support</artifactId> <version>3.2.6.RELEASE</version> </dependency>
二、示例代码
ehcache.xml代码如下：
<?xml version="1.0" encoding="UTF-8"?> <ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://ehcache.org/ehcache.xsd" updateCheck="false"> <!-- 默认缓存配置 ，缓存名称为 default --> <defaultCache maxElementsInMemory="50" eternal="false" overflowToDisk="false" memoryStoreEvictionPolicy="LFU" /> <!-- 自定义缓存，名称为lt.ehcache --> <cache name="lt.ecache" maxElementsInMemory="50" eternal="false" overflowToDisk="false" memoryStoreEvictionPolicy="LFU" /> </ehcache>
Spring-config-ehcache.xml代码如下：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:cache="http://www.springframework.org/schema/cache" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/cache http://www.springframework.org/schema/cache/spring-cache.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"> <cache:annotation-driven /> <context:component-scan base-package="com.ehcache.test" /> <!-- 注解扫描路径 --> <bean id="cacheManager" class="org.springframework.cache.ehcache.EhCacheCacheManager"> <property name="cacheManager" ref="ehcache" /> </bean> <bean id="ehcache" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean"> <property name="configLocation" value="classpath:ehcache.xml" /> </bean> </beans>
ehcache.xml与Spring-config-ehcache.xml存放在系统目录下。
相关代码如下：
实体Employee.java
1 package com.ehcache.test; 2 3 import java.io.Serializable; 4 5 public class Employee implements Serializable { 6 private static final long serialVersionUID = -6534180255882276966L; 7 private int id; 8 private String name; 9 private String designation; 10 11 public Employee(int id, String name, String designation) { 12 super(); 13 this.id = id; 14 this.name = name; 15 this.designation = designation; 16 } 17 18 public int getId() { 19 return id; 20 } 21 22 public void setId(int id) { 23 this.id = id; 24 } 25 26 @Override 27 public String toString() { 28 return "Employee [id=" + id + ", name=" + name + ", designation=" + designation + "]"; 29 } 30 31 public String getName() { 32 return name; 33 } 34 35 public void setName(String name) { 36 this.name = name; 37 } 38 39 public String getDesignation() { 40 return designation; 41 } 42 43 public void setDesignation(String designation) { 44 this.designation = designation; 45 } 46 }
EmployeeDAO.java
1 package com.ehcache.test; 2 3 import java.util.ArrayList; 4 import java.util.List; 5 6 import org.springframework.cache.annotation.CacheEvict; 7 import org.springframework.cache.annotation.CachePut; 8 import org.springframework.cache.annotation.Cacheable; 9 import org.springframework.stereotype.Component; 10 11 @Component("employeeDAO") 12 public class EmployeeDAO { 13 14 // key 当前类，缓存对象为返回值list 15 @Cacheable(value = {"lt.ecache"}, key = "#root.targetClass") 16 public List<Employee> getEmployees() { 17 System.out.println("*** getEmployees() 已经调用 ***"); 18 List<Employee> list = new ArrayList<Employee>(5); 19 list.add(new Employee(1, "Ben", "Architect")); 20 list.add(new Employee(2, "Harley", "Programmer")); 21 list.add(new Employee(3, "Peter", "BusinessAnalyst")); 22 list.add(new Employee(4, "Sasi", "Manager")); 23 list.add(new Employee(5, "Abhi", "Designer")); 24 return list; 25 } 26 27 // key id，缓存数据为返回值Employee对象 28 @Cacheable(value = "lt.ecache", key = "#id") 29 public Employee getEmployee(int id, List<Employee> employees) { 30 System.out.println("*** getEmployee(): " + id + " ***"); 31 Employee emp = null; 32 for (Employee employee : employees) { 33 if (employee.getId() == id) { 34 emp = employee; 35 } 36 } 37 return emp; 38 } 39 40 // @CachePut会去替换缓存中的Employee对象为当前id对应的对象 41 @CachePut(value = "lt.ecache", key = "#id") 42 public Employee updateEmployee(int id, String designation, List<Employee> employees) { 43 System.out.println("*** updateEmployee() " + id + " ***"); 44 Employee emp = null; 45 int i = 0; 46 for (Employee employee : employees) { 47 if (employee.getId() == id) { 48 employee.setDesignation(designation); 49 emp = employee; 50 } 51 } 52 System.out.println(emp); 53 return emp; 54 } 55 56 //key为参数中Employee对象的id，缓存指定id对应的Employee对象 57 @Cacheable(value = "lt.ecache", key = "#employee.id") 58 public Employee addEmployee(Employee employee, List<Employee> employees) { 59 System.out.println("*** addEmployee() : " + employee.getId() + " ***"); 60 employees.add(employee); 61 System.out.println(employee); 62 return employee; 63 } 64 65 //key为参数中的id，移除缓存，移除指定id对应的Employee对象 66 @CacheEvict(value = "lt.ecache", key = "#id") 67 public Employee removeEmployee(int id, List<Employee> employees) { 68 System.out.println("*** removeEmployee() : " + id + " ***"); 69 Employee emp = null; 70 int i = 0; 71 for (Employee employee : employees) { 72 if (employee.getId() == id) { 73 emp = employee; 74 } else { 75 i++; 76 } 77 } 78 employees.remove(i); 79 return emp; 80 } 81 82 //key为当前类，移除缓存，移除employees列表对象 83 @CacheEvict(value = "lt.ecache", key = "#root.targetClass") 84 public List<Employee> removeAllEmployee(List<Employee> employees) { 85 System.out.println("*** removeAllEmployee() : ***"); 86 employees.clear(); 87 System.out.println(employees.size()); 88 return employees; 89 } 90 91 }
lt.ecache为ehcache.xml中配置的缓存名称。对于要使用到缓存的方法必须使用@注解，同时还要将缓存对象在方法的最后return，否则会报错。
类中使用到了Spring Expression Language（SpEL）,其中相关说明如下
#root.methodName 被执行方法的名称
#root.method.name 被执行的方法
#root.target 被执行的目标对象
#root.targetClass 被执行的目标对象的class
#root.args[0] 调用目标方法的时候目标方法里面的参数（可将参数列表类比成对象数组）的第一个
#root.caches[0].name 获取当前执行方法的缓存
Main.java
1 package com.ehcache.test; 2 3 import java.util.List; 4 5 import org.springframework.context.ApplicationContext; 6 import org.springframework.context.support.ClassPathXmlApplicationContext; 7 8 9 public class Main { 10 11 public static void main(String[] args) { 12 13 ApplicationContext context = new ClassPathXmlApplicationContext("spring-config-ehcache.xml"); 14 15 EmployeeDAO dao = (EmployeeDAO) context.getBean("employeeDAO"); 16 17 System.out.println("-----------------------第1次调用----------------------------"); 18 List<Employee> employees = dao.getEmployees(); 19 System.out.println(employees.toString()); 20 System.out.println("------------------------第2次调用---------------------------"); 21 employees = dao.getEmployees(); 22 System.out.println(employees.toString()); 23 System.out.println("------------------------第3次调用---------------------------"); 24 employees = dao.getEmployees(); 25 System.out.println(employees.toString()); 26 27 28 System.out.println("-------------------------第1次调用--------------------------"); 29 Employee employee = dao.getEmployee(1, employees); 30 System.out.println(employee.toString()); 31 System.out.println("-------------------------第2次调用--------------------------"); 32 employee = dao.getEmployee(1, employees); 33 System.out.println(employee.toString()); 34 35 36 System.out.println("------------------------- 对象更新--------------------------"); 37 dao.updateEmployee(1, "已经更新的对象", employees); 38 System.out.println("-------------------------第1次调用--------------------------"); 39 employee = dao.getEmployee(1, employees); 40 System.out.println(employee.toString()); 41 System.out.println("-------------------------第2次调用--------------------------"); 42 employee = dao.getEmployee(1, employees); 43 System.out.println(employee.toString()); 44 45 46 System.out.println("------------------------- 添加对象--------------------------"); 47 dao.addEmployee(new Employee(6, "555", "Designer5555"),employees); 48 System.out.println("-------------------------第1次调用--------------------------"); 49 employee = dao.getEmployee(6, employees); 50 System.out.println(employee); 51 System.out.println("-------------------------第2次调用--------------------------"); 52 employee = dao.getEmployee(6, employees); 53 System.out.println(employee.toString()); 54 55 56 System.out.println("------------------------- 清除一个对象--------------------------"); 57 System.out.println(employees.size()); 58 employee = dao.removeEmployee(6, employees); 59 System.out.println("-------------------------第1次调用--------------------------"); 60 employees = dao.getEmployees(); 61 System.out.println(employees); 62 System.out.println(employees.size()); 63 System.out.println("-------------------------第2次调用--------------------------"); 64 employees = dao.getEmployees(); 65 System.out.println(employees); 66 67 68 System.out.println("------------------------- 清除所有--------------------------"); 69 System.out.println(employees.size()); 70 employees = dao.removeAllEmployee(employees); 71 System.out.println("-------------------------第1次调用--------------------------"); 72 employees = dao.getEmployees(); 73 System.out.println(employees); 74 System.out.println("-------------------------第2次调用--------------------------"); 75 employees = dao.getEmployees(); 76 System.out.println(employees); 77 } 78 }
当对象缓存之后方法就不会执行，而是直接从缓存中获取。
