在实际项目开发中，会使用到很多缓存技术，而且数据库的设计一般也会依赖于有缓存的情况下设计。
- 常用的缓存分两种：本地缓存和分布式缓存。
- 常用的本地缓存是guava cache，本文主要介绍guava cache在项目中的使用，首先来了解下为什么使用缓存，以数据库（如MYSQL）、本地缓存（如guava cache）及分布式缓存（如redis）的区别来讲：
一、数据库、本地缓存及分布式缓存的区别
1、存储位置：
- 数据库:任何机器硬盘，开关机时，数据不丢失
- 本地缓存：本机内存，一旦关机，之前的数据丢失
- 分布式缓存（如redis）：存在redis所在机器的内存，一旦redis所在机器关机，数据丢失
2、持久化：
- 数据库:可以持久化
- 本地缓存：不可以持久化
- 分布式缓存（如redis）：不可以持久化
3、访问速度：
- 数据库:慢
- 本地缓存：最快
- 分布式缓存：快
4、扩展性：
- 数据库:可扩展，可存在其他机器的硬盘
- 本地缓存：不可扩展，只能存在本机内存
- 分布式缓存：可扩展，可存在其他机器的内存
5、使用场景：
- 数据库:需要实现持久化保存
- 本地缓存：需要快速访问，但需要考虑内存大小
- 分布式缓存：1）需要快速访问，不需要考虑内存大小
2）需要实现持久化，但会丢失一些数据
3）需要让缓存集中在一起，访问任一机器上内存中的数据都可以从缓存中得到
二、实例
基于SSMM框架整合步骤，连接（）的flowershop项目。
1、启动MYSQL
2、创建mvn项目
- 配置pom.xml文件（这里直接给出已经配置好的）
-
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4 5 4.0.0 6 7com.wn 8flowershop 91.0-SNAPSHOT 10flowershop 11war 1213 221.8 14UTF-8 15UTF-8 164.2.4.RELEASE 173.2.8 181.2.2 192.6.4 203.1.0 2123 24 11125 30 31javax.servlet 26javax.servlet-api 27${servlet-api.version} 28provided 2932 36org.springframework 33spring-core 34${spring.version} 3537 41org.springframework 38spring-beans 39${spring.version} 4042 46 47org.springframework 43spring-context 44${spring.version} 4548 52org.springframework 49spring-web 50${spring.version} 5153 57 58org.springframework 54spring-webmvc 55${spring.version} 5659 63 64org.springframework 60spring-jdbc 61${spring.version} 6265 70 71mysql 66mysql-connector-java 675.1.27 68runtime 6972 76 77org.apache.tomcat 73tomcat-jdbc 747.0.47 7578 82 83org.mybatis 79mybatis 80${mybatis.version} 8184 88 89org.mybatis 85mybatis-spring 86${mybatis-spring.version} 8790 94com.fasterxml.jackson.core 91jackson-annotations 92${jackson.version} 9395 99com.fasterxml.jackson.core 96jackson-core 97${jackson.version} 98100 104 105com.fasterxml.jackson.core 101jackson-databind 102${jackson.version} 103106 110com.google.guava 107guava 10814.0.1 109112 124113 123114 122org.apache.maven.plugins 115maven-compiler-plugin 116117 1211.8118 1.8 119utf-8 120这里用到guava cache，所以别忘了引入依赖guava cache
-
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3 com.google.guava 4guava 514.0.1 6 - 引入mysql库配置（src/main/resources）
jdbc.properties
1 jdbc.driverClassName = com.mysql.jdbc.Driver2 jdbc.url = jdbc:mysql://localhost:3306/wn3 jdbc.username = root4 jdbc.password = 123456
- 引入spring配置文件（src/main/resources）
spring.xml
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10 11 12 21 26 27 2822 23 24 25 29 3630 31 35- 32
classpath*:mapper/*Mapper.xml 3337 4038 39 -
创建基本包（package）结构（controller、service、dao、mapper、model）
- 创建src/main/resources/mapper的folder包，用于放置*Mapper.xml
-
配置web.xml，使spring生效
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5 6 14dispatcherServlet 7org.springframework.web.servlet.DispatcherServlet 89 12contextConfigLocation 10classpath*:spring*.xml 111 1315 18 19dispatcherServlet 16/ 1720 31encodingFilter 21org.springframework.web.filter.CharacterEncodingFilter 2223 26encoding 24UTF-8 2527 30forceEncoding 28true 2932 35encodingFilter 33/* 34
3、使用mybatis-generator创建mybatis的xml文件、mapper层接口、model层
- 将生成的类、接口、xml拷贝到项目中
- FlowerMapper.xml
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4 5 126 7 8 9 10 11 13 id, type, colour, number, price, florescence 14 15 22 29 30 54 6162 delete from 63 t_flower 64 where id = #{id,jdbcType=INTEGER} 65 6667 insert into t_flower (id, 68 type, colour, 69 number, price, florescence 70 ) 71 values 72 (#{id,jdbcType=INTEGER}, #{type,jdbcType=VARCHAR}, 73 #{colour,jdbcType=VARCHAR}, 74 #{number,jdbcType=INTEGER}, 75 #{price,jdbcType=DECIMAL}, #{florescence,jdbcType=INTEGER} 76 ) 77 7879 insert into t_flower 80 12181 10082 id, 83 8485 type, 86 8788 colour, 89 9091 number, 92 9394 price, 95 9697 florescence, 98 99101 120102 #{id,jdbcType=INTEGER},103 104105 #{type,jdbcType=VARCHAR},106 107108 #{colour,jdbcType=VARCHAR},109 110111 #{number,jdbcType=INTEGER},112 113114 #{price,jdbcType=DECIMAL},115 116117 #{florescence,jdbcType=INTEGER},118 119122 update t_flower123 142124 140 where id = #{id,jdbcType=INTEGER}141125 type = #{type,jdbcType=VARCHAR},126 127128 colour = #{colour,jdbcType=VARCHAR},129 130131 number = #{number,jdbcType=INTEGER},132 133134 price = #{price,jdbcType=DECIMAL},135 136137 florescence = #{florescence,jdbcType=INTEGER},138 139143 update t_flower144 set type = #{type,jdbcType=VARCHAR},145 colour =146 #{colour,jdbcType=VARCHAR},147 number = #{number,jdbcType=INTEGER},148 price =149 #{price,jdbcType=DECIMAL},150 florescence =151 #{florescence,jdbcType=INTEGER}152 where id = #{id,jdbcType=INTEGER}153 154
- Flower
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1 package com.wn.model; 2 3 public class Flower { 4 private Integer id; 5 6 private String type; 7 8 private String colour; 9 10 private Integer number;11 12 private Long price;13 14 private Integer florescence;15 16 public Integer getId() {17 return id;18 }19 20 public void setId(Integer id) {21 this.id = id;22 }23 24 public String getType() {25 return type;26 }27 28 public void setType(String type) {29 this.type = type == null ? null : type.trim();30 }31 32 public String getColour() {33 return colour;34 }35 36 public void setColour(String colour) {37 this.colour = colour == null ? null : colour.trim();38 }39 40 public Integer getNumber() {41 return number;42 }43 44 public void setNumber(Integer number) {45 this.number = number;46 }47 48 public Long getPrice() {49 return price;50 }51 52 public void setPrice(Long price) {53 this.price = price;54 }55 56 public Integer getFlorescence() {57 return florescence;58 }59 60 public void setFlorescence(Integer florescence) {61 this.florescence = florescence;62 }63 }
- FlowerMapper.java
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1 package com.wn.mapper; 2 3 import java.util.List; 4 5 import org.apache.ibatis.annotations.Param; 6 7 import com.wn.model.Flower; 8 9 public interface FlowerMapper {10 int deleteByPrimaryKey(Integer id);11 12 int insert(Flower record);13 14 int insertSelective(Flower record);15 16 Flower selectByPrimaryKey(Integer id);17 18 ListselectByCondition(Flower record);19 20 List selectLimit(@Param("start") int start, @Param("size") int size);21 22 int updateByPrimaryKeySelective(Flower record);23 24 int updateByPrimaryKey(Flower record);25 26 List selectByColour(String colour);27 }
4、编写dao、service、controller
- FlowerDao
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1 package com.wn.dao; 2 3 import java.util.List; 4 5 import org.springframework.beans.factory.annotation.Autowired; 6 import org.springframework.stereotype.Repository; 7 8 import com.wn.mapper.FlowerMapper; 9 import com.wn.model.Flower;10 11 @Repository12 public class FlowerDao {13 @Autowired14 private FlowerMapper flowerMapper;15 16 public boolean add(Flower flower) {17 return flowerMapper.insert(flower) == 1 ? true : false;18 }19 20 public Flower getById(Integer id) {21 return flowerMapper.selectByPrimaryKey(id);22 }23 24 public boolean deleteById(Integer id) {25 return flowerMapper.deleteByPrimaryKey(id) == 1 ? true : false;26 }27 28 public boolean update(Flower flower) {29 return flowerMapper.updateByPrimaryKey(flower) == 1 ? true : false;30 }31 32 public boolean update2(Flower flower) {33 return flowerMapper.updateByPrimaryKeySelective(flower) == 1 ? true : false;34 }35 36 /*37 * 实现条件不定查询38 */39 public ListgetByCondition(Flower flower) {40 return flowerMapper.selectByCondition(flower);41 }42 43 /*44 * 传入开始显示记录的索引，即显示记录的条数，实现分页显示功能45 */46 public List selectLimit(int start, int size) {47 return flowerMapper.selectLimit(start, size);48 }49 50 public List selectByColour(String colour) {51 return flowerMapper.selectByColour(colour);52 }53 } - FlowerService
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1 package com.wn.service; 2 3 import java.util.List; 4 import java.util.concurrent.ExecutionException; 5 import java.util.concurrent.TimeUnit; 6 7 import org.springframework.beans.factory.annotation.Autowired; 8 import org.springframework.stereotype.Service; 9 10 import com.google.common.cache.CacheBuilder;11 import com.google.common.cache.CacheLoader;12 import com.google.common.cache.LoadingCache;13 import com.wn.dao.FlowerDao;14 import com.wn.model.Flower;15 16 @Service17 public class FlowerService {18 @Autowired19 private FlowerDao flowerDao;20 21 public boolean addFlower(String type, String colour, Integer number, long price, Integer florescence) {22 Flower flower = new Flower();23 flower.setType(type);24 flower.setColour(colour);25 flower.setNumber(number);26 flower.setPrice(price);27 flower.setFlorescence(florescence);28 return flowerDao.add(flower);29 }30 31 public Flower getFlower(Integer id) {32 return flowerDao.getById(id);33 }34 35 public boolean deleteFlower(Integer id) {36 return flowerDao.deleteById(id);37 }38 39 public boolean updateFlower(Integer id, String type, String colour, Integer number, Long price,40 Integer florescence) {41 Flower flower = flowerDao.getById(id);42 flower.setType(type);43 flower.setColour(colour);44 flower.setNumber(number);45 flower.setPrice(price);46 flower.setFlorescence(florescence);47 return flowerDao.update(flower);48 }49 50 public boolean updateFlower2(Integer id, String type, String colour, Integer number, Long price,51 Integer florescence) {52 Flower flower = flowerDao.getById(id);53 flower.setType(type);54 flower.setColour(colour);55 flower.setNumber(number);56 flower.setPrice(price);57 flower.setFlorescence(florescence);58 return flowerDao.update2(flower);59 }60 61 public ListgetFlowerByCondition(String type, String colour, Integer number, Long price,62 Integer florescence) {63 Flower flower = new Flower();64 flower.setColour(colour);65 flower.setType(type);66 flower.setNumber(number);67 flower.setPrice(price);68 flower.setFlorescence(florescence);69 return flowerDao.getByCondition(flower);70 }71 72 public List selectLimit(Integer start, Integer size) {73 return flowerDao.selectLimit(start, size);74 }75 76 /**本地缓存-guava cache的流程：77 * 1、从guava cache中获取 -- flowerCache.get(colour) 78 * 2、如果存在，直接返回数据给controller79 * 3、如果不存在，调用load方法（先从mysql获取，再存入guava cache，最后从guava80 * cache读出该数据，返回给controller）81 */82 public List getFlowerWithCache(String colour) {83 List flowerList = null;84 try {85 flowerList = flowerCache.get(colour);86 } catch (ExecutionException e) {87 e.printStackTrace();88 }89 return flowerList;90 }91 LoadingCache load(String colour) {94 System.out.println("从数据库查");95 return flowerDao.selectByColour(colour);96 }97 });98 } - FlowerController
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1 package com.wn.controller; 2 3 import java.util.List; 4 5 import org.springframework.beans.factory.annotation.Autowired; 6 import org.springframework.web.bind.annotation.PathVariable; 7 import org.springframework.web.bind.annotation.RequestMapping; 8 import org.springframework.web.bind.annotation.RequestMethod; 9 import org.springframework.web.bind.annotation.RequestParam;10 import org.springframework.web.bind.annotation.RestController;11 12 import com.wn.model.Flower;13 import com.wn.service.FlowerService;14 15 @RestController16 @RequestMapping("/flower")17 public class FlowerController {18 @Autowired19 private FlowerService flowerService;20 21 @RequestMapping(value = "/add", method = RequestMethod.POST)22 public boolean addFlower(@RequestParam("type") String type, @RequestParam("colour") String colour,23 @RequestParam("number") Integer number, @RequestParam("price") Long price,24 @RequestParam("florescence") Integer florescence) {25 return flowerService.addFlower(type, colour, number, price, florescence);26 }27 28 @RequestMapping(value = "/get", method = RequestMethod.GET)29 public Flower getFlower(Integer id) {30 return flowerService.getFlower(id);31 }32 33 @RequestMapping(value = "/delete/{id}", method = RequestMethod.DELETE)34 public boolean deleteFlower(@PathVariable("id") Integer id) {35 return flowerService.deleteFlower(id);36 }37 38 @RequestMapping(value = "/update", method = RequestMethod.PUT)39 public boolean updateFlower(@RequestParam(value = "id") Integer id,40 @RequestParam(value = "type", required = false) String type,41 @RequestParam(value = "colour", required = false) String colour,42 @RequestParam(value = "number", required = false) Integer number,43 @RequestParam(value = "price", required = false) Long price,44 @RequestParam(value = "florescence", required = false) Integer florescence) {45 46 return flowerService.updateFlower(id, type, colour, number, price, florescence);47 }48 49 @RequestMapping(value = "/update2", method = RequestMethod.PUT)50 public boolean updateFlower2(@RequestParam(value = "id") Integer id,51 @RequestParam(value = "type", required = false) String type,52 @RequestParam(value = "colour", required = false) String colour,53 @RequestParam(value = "number", required = false) Integer number, @RequestParam(value = "price") Long price,54 @RequestParam(value = "florescence", required = false) Integer florescence) {55 return flowerService.updateFlower2(id, type, colour, number, price, florescence);56 }57 58 @RequestMapping(value = "/getFlowerByConditon", method = RequestMethod.GET)59 public ListgetFlowerByCondition(@RequestParam(value = "type", required = false) String type,60 @RequestParam(value = "colour", required = false) String colour,61 @RequestParam(value = "number", required = false) Integer number,62 @RequestParam(value = "price", required = false) Long price,63 @RequestParam(value = "florescence", required = false) Integer florescence) {64 return flowerService.getFlowerByCondition(type, colour, number, price, florescence);65 }66 67 @RequestMapping(value = "/getFlowerByLimit", method = RequestMethod.GET)68 public List getFlowerByLimit(@RequestParam("start") Integer start, @RequestParam("size") Integer size) {69 return flowerService.selectLimit(start, size);70 }71 72 // 从本地缓存获取数据，若本地缓存没有，再从数据库获取73 @RequestMapping(value = "/getWithCache", method = RequestMethod.GET)74 public List getWithCache(@RequestParam("colour") String colour) {75 return flowerService.getFlowerWithCache(colour);76 }77 }