企业项目开发--本地缓存guava cache（1）

        <!-- guava cache -->
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>14.0.1</version>
        </dependency>

package com.xxx.mapper.userManagement;

import java.util.List;

import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

import com.xxx.model.userManagement.Admin;

/**
 * 管理员Mapper
 */
public interface AdminMapper {
    
    /**************注解**************/
    @Insert("INSERT INTO userinfo(username, password) VALUES(#{username},#{password})")
    public int insertAdmin(Admin admin);

    @Select("SELECT * FROM userinfo WHERE username = #{username} AND password = #{password}")
    @Results(value = { 
            @Result(id = true, column = "id", property = "id"),
            @Result(column = "username", property = "username"),
            @Result(column = "password", property = "password") })
    public Admin selectAdmin(@Param("username") String username,
                             @Param("password") String password);
    
    /***************xml**************/
    /**
     * 条件不定式查询
     * 我们这里使用@Param指定参数，这样的话，在AdminMapper.xml中就不用再使用parameterType属性了；否则得写parameterType属性
     */
    public List<Admin> getAdminByConditions(@Param("username")String username,
                                            @Param("password")String password, 
                                            @Param("start")int start, 
                                            @Param("limit")int limit);
    
    /**
     * 返回主键
     */
    public int insertAdminWithBackId(Admin admin);
    
    /****************guava cache*****************/
    @Select("SELECT * FROM userinfo WHERE username = #{username}")
    @Results(value = { 
            @Result(id = true, column = "id", property = "id"),
            @Result(column = "username", property = "username"),
            @Result(column = "password", property = "password") })
    public List<Admin> getUserByName(@Param("username") String username);
}

package com.xxx.dao.userManagement;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

import com.xxx.mapper.userManagement.AdminMapper;
import com.xxx.model.userManagement.Admin;

/**
 * 管理员DAO
 */
@Repository
public class AdminDao {
    @Autowired
    private AdminMapper adminMapper;
    /***************注解*****************/
    public boolean register(Admin admin){
        return adminMapper.insertAdmin(admin)==1?true:false;
    }
    
    public Admin login(String username ,String password){
        return adminMapper.selectAdmin(username, password);
    }
    /****************xml******************/
    public List<Admin> findAdmin(String username, String password, int start, int limit){
        return adminMapper.getAdminByConditions(username, password, start, limit);
    }
    
    public int insertAdminWithBackId(Admin admin){
        return adminMapper.insertAdminWithBackId(admin);
    }
    /******************guava cache********************/
    public List<Admin> getUserByName(String username){
        return adminMapper.getUserByName(username);
    }
}

package com.xxx.service.userManagement;

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

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.xxx.dao.userManagement.AdminDao;
import com.xxx.model.userManagement.Admin;
import com.xxx.vo.userManagement.AdminCacheKey;

/**
 * 管理员service
 */
@Service
public class AdminService {
    @Autowired
    private AdminDao adminDao;

    public boolean register(Admin admin) {
        return adminDao.register(admin);
    }

    public Admin login(String username, String password) {
        return adminDao.login(username, password);
    }

    /*********** 以下方法是为了测试mybatis中使用xml **********/
    public List<Admin> findAdmin(String username, 
                                 String password, 
                                 int start,
                                 int limit) {
        return adminDao.findAdmin(username, password, start, limit);
    }

    public Admin insertAdminWithBackId(Admin admin) {
        int record = adminDao.insertAdminWithBackId(admin);
        if (record == 1) {
            return admin;// 这时的admin已经被赋予主键了
        }
        return null;
    }

    /************************ guava cache *************************/
    /************单条件的查询，key为String***********/
    public List<Admin> findByUsername(String username) {
        List<Admin> adminList = null;
        try {
            adminList = adminListCache.get(username);
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
        return adminList;
    }

    LoadingCache<String, List<Admin>> adminListCache = CacheBuilder.newBuilder()
            .expireAfterWrite(20, TimeUnit.MINUTES)// 缓存20分钟
            .maximumSize(1000)// 最多缓存1000个对象
            .build(new CacheLoader<String, List<Admin>>() {
                public List<Admin> load(String username) throws Exception {
                    return adminDao.getUserByName(username);
                }
            });

    /************多条件的查询，key为Object（封装了多个条件的VO类）***********/
    public List<Admin> findAdminList(String username, 
                                     String password,
                                     int start, 
                                     int limit) {
        /*
         * 注意：
         * 如果以一个新建的对象做为key的话，因为每次都是新建一个对象，所以这样的话，实际上每次访问key都是不同的，即每次访问都是重新进行缓存;
         * 但是实际上，我们想要根据对象的属性来判断对象是否相等，只需要根据这些属性重写对象的hashCode与equals方法即可，
         * 所以重写了AdminCacheKey类的hashCode和equals方法，这样，每次访问的话，就会以每个条件是否相等来判断对象（即key）是否相等了，这一块儿的缓存就会起作用了
         */
        AdminCacheKey cacheKey = new AdminCacheKey(username, 
                                                   password, 
                                                   start,
                                                   limit);
        List<Admin> adminList = null;
        try {
            System.out.println(cacheKey);
            adminList = adminsCache.get(cacheKey);
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
        return adminList;
    }

    LoadingCache<AdminCacheKey, List<Admin>> adminsCache = CacheBuilder.newBuilder()
            .expireAfterWrite(60, TimeUnit.MINUTES) // 缓存项在给定时间内（60min）没有被写访问（创建或覆盖），则回收
            .maximumSize(100) // 最多缓存100项
            .build(new CacheLoader<AdminCacheKey, List<Admin>>() {
                public List<Admin> load(AdminCacheKey key) throws Exception {
                    return adminDao.findAdmin(key.getUsername(),
                                              key.getPassword(), 
                                              key.getStart(), 
                                              key.getLimit());
                }
            });

}