# 功能

简单实现数据的缓存，提供了一些基本的缓存特性设置（如过期时间等）

# demo 描述

为 3 张表数据做缓存：公司表、部门表、员工表，使用时通过不同的键值调用此缓存；代码中涉及到多线程访问缓存，可以自己切换线程，更好说明一些；

# 程序示例

	package com.example.google.guava.demo.cache;

	import com.example.google.guava.demo.model.Company;
	import com.example.google.guava.demo.model.Department;
	import com.example.google.guava.demo.model.Employee;
	import com.google.common.cache.Cache;
	import com.google.common.cache.CacheBuilder;

	import java.util.ArrayList;
	import java.util.List;
	import java.util.concurrent.Callable;
	import java.util.concurrent.ExecutionException;
	import java.util.concurrent.TimeUnit;

	/**
	* <p>
	* <code>CacheTest</code>
	* </p>
	* Description: 以员工表、部门表、公司表三张表的缓存为例
	*
	* @author Mcchu
	* @date 2017/10/20 9:34
	*/
	public class CacheTest<K,V> {

	private Cache<K, V> cache= CacheBuilder
	.newBuilder()
	.maximumSize(2)
	.expireAfterWrite(10, TimeUnit.MINUTES)
	.build();


	@SuppressWarnings("unchecked")
	private Object getCache(K key,final String threadName){
	Object value=null;

	try {
	System.out.println("线程："+threadName+"获取数据");

	// 根据不同的 key 获取缓存数据
	if ( "company".equals(key) ){
	Callable callable = ()->{
	System.out.println("###获取公司缓存数据###");
	return (List<Company>) getCompanyCacheList();
	};
	value = cache.get(key,callable);
	}
	if ( "department".equals(key) ){
	Callable callable = ()->{
	System.out.println("###获取部门缓存数据###");
	return (List<Department>) getDepartmentCacheList();
	};
	value = cache.get(key,callable);
	}
	if ( "employee".equals(key) ){
	Callable callable = ()->{
	System.out.println("###获取人员缓存数据###");
	return (List<Employee>) getEmployeeCacheList();
	};
	value = cache.get(key,callable);
	}

	// 下面是 java7
	/*value = cache.get (key, new Callable<V>() {
	public V call () {
	System.out.println ("### 获取缓存数据 ###");
	return (V) "dataValue";
	}
	});*/
	} catch (ExecutionException e) {
	e.printStackTrace();
	}

	return value;
	}


	public static void main(String[] args) {
	final CacheTest<String,String> cacheTest=new CacheTest<String,String>();

	Runnable task1 = () -> {
	System.out.println("线程t1开始");
	Object value=cacheTest.getCache("company","T1");
	System.out.println("线程t1获取到的缓存值："+value);
	System.out.println("线程t1开始");
	};
	new Thread(task1).start();

	Runnable task2 = () -> {
	System.out.println("线程t2开始");
	Object value=cacheTest.getCache("department","T2");
	System.out.println("线程t2获取到的缓存值："+value);
	System.out.println("线程t2结束");
	};
	new Thread(task2).start();

	Runnable task3 = () -> {
	System.out.println("线程t3开始");
	Object value=cacheTest.getCache("department","T3");
	System.out.println("线程t3获取到的缓存值："+value);
	System.out.println("线程t3结束");
	};
	new Thread(task3).start();


	// 下面是 java7，等同于上面代码
	/*Thread t1=new Thread (new Runnable () {
	@Override
	public void run () {
	System.out.println ("线程 t1 开始");
	Object value=cacheTest.getCache ("key1","T1");
	System.out.println ("线程 t1 获取到的缓存值："+value);
	System.out.println ("线程 t1 开始");
	}
	});
	Thread t2=new Thread (new Runnable () {
	@Override
	public void run () {
	System.out.println ("线程 t2 开始");
	Object value=cacheTest.getCache ("key1","T2");
	System.out.println ("线程 t2 获取到的缓存值："+value);
	System.out.println ("线程 t2 结束");
	}
	});
	Thread t3=new Thread (new Runnable () {
	@Override
	public void run () {
	System.out.println ("线程 t3 开始");
	Object value=cacheTest.getCache ("key3","T3");
	System.out.println ("线程 t3 获取到的缓存值："+value);
	System.out.println ("线程 t3 结束");
	}
	});
	t1.start ();
	t2.start ();
	t3.start ();*/
	}

	/**
	* 员工假数据（实际来源可能是数据库或远程接口）
	* @return 人员列表
	*/
	private static List<Employee> getEmployeeCacheList(){
	List<Employee> employeeList = new ArrayList<>();
	Employee employee1 = new Employee("Jalen","102","20171121");
	Employee employee2 = new Employee("Jermy","101","20171122");
	Employee employee3 = new Employee("Abely","104","20171123");
	Employee employee4 = new Employee("Mercy","103","20171124");
	employeeList.add(employee1);
	employeeList.add(employee2);
	employeeList.add(employee3);
	employeeList.add(employee4);
	return employeeList;
	}

	/**
	* 部门假数据（实际来源可能是数据库或远程接口）
	* @return 部门列表
	*/
	private static List<Department> getDepartmentCacheList(){
	List<Department> departmentList = new ArrayList<>();
	Department department1 = new Department("101","采购部","1");
	Department department2 = new Department("102","财务部","1");
	Department department3 = new Department("103","信管部","1");
	Department department4 = new Department("104","外贸部","1");
	departmentList.add(department1);
	departmentList.add(department2);
	departmentList.add(department3);
	departmentList.add(department4);
	return departmentList;
	}

	/**
	* 公司假数据（实际来源可能是数据库或远程接口）
	* @return 公司列表
	*/
	private static List<Company> getCompanyCacheList(){
	List<Company> companyList = new ArrayList<>();
	Company company1 = new Company("1","Sanmina");
	Company company2 = new Company("2","Google");
	Company company3 = new Company("3","Tecent");
	companyList.add(company1);
	companyList.add(company2);
	companyList.add(company3);
	return companyList;
	}
	}

# 公司实体类

	package com.example.google.guava.demo.model;

	import lombok.AllArgsConstructor;
	import lombok.Data;
	import lombok.NoArgsConstructor;

	/**
	* <p>
	* <code>Company</code>
	* </p>
	* Description:
	*
	* @author Mcchu
	* @date 2017/10/20 10:14
	*/
	@Data
	@AllArgsConstructor
	@NoArgsConstructor
	public class Company {

	private String companyId;

	private String companyName;
	}

# 部门实体类

	package com.example.google.guava.demo.model;

	import lombok.AllArgsConstructor;
	import lombok.Data;
	import lombok.NoArgsConstructor;

	/**
	* <p>
	* <code>Department</code>
	* </p>
	* Description:
	*
	* @author Mcchu
	* @date 2017/10/20 10:10
	*/
	@Data
	@NoArgsConstructor
	@AllArgsConstructor
	public class Department {

	private String departmentId;

	private String departmentName;

	private String companyId;
	}

# 员工实体类

	package com.example.google.guava.demo.model;

	import lombok.AllArgsConstructor;
	import lombok.Data;
	import lombok.NoArgsConstructor;

	/**
	* <p>
	* <code>Employee</code>
	* </p>
	* Description:
	*
	* @author Mcchu
	* @date 2017/10/20 9:19
	*/
	@Data
	@AllArgsConstructor
	@NoArgsConstructor
	public class Employee {

	String name;

	String departmentId;

	String employeeId;
	}

# 输出结果

如上，当线程 2 运行过后，部门数据已经缓存到 cache 对象当中，当线程 3 再去获取时，就可以直接从缓存中获取数据了

线程t2开始
线程t3开始
线程：T2获取数据
线程t1开始
线程：T3获取数据
线程：T1获取数据
###获取部门缓存数据###
线程t2获取到的缓存值：[Department(departmentId=101, departmentName=采购部, companyId=1), Department(departmentId=102, departmentName=财务部, companyId=1), Department(departmentId=103, departmentName=信管部, companyId=1), Department(departmentId=104, departmentName=外贸部, companyId=1)]
线程t2结束
###获取公司缓存数据###
线程t3获取到的缓存值：[Department(departmentId=101, departmentName=采购部, companyId=1), Department(departmentId=102, departmentName=财务部, companyId=1), Department(departmentId=103, departmentName=信管部, companyId=1), Department(departmentId=104, departmentName=外贸部, companyId=1)]
线程t3结束
线程t1获取到的缓存值：[Company(companyId=1, companyName=Sanmina), Company(companyId=2, companyName=Google), Company(companyId=3, companyName=Tecent)]
线程t1开始

# 参考

http://blog.csdn.net/michaelwubo/article/details/50865185

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