前言：推荐系统的输入是必要的 ,这些数据是推荐的基础。因为非常熟悉的推荐系统引擎将item(物品)推荐给user(用户)，很容易的认为偏好(Preference)是user和item之间的联系。偏好包含了一个user ID和一个item ID，通常情况下，一个数值代表了user对item偏好的强度。Mahout中ID都是数值，实际上是整数（lang型）。偏好值可以是任何值，值越大代表这正向偏好 越大。例如，这些值可能是1到5的打分，user将1给于他不喜欢的，5给他很喜欢的。
基础数据：intro.csv
1,101,5.0
1,102,3.0
1,103,2.52,101,2.0
2,102,2.5
2,103,5.0
2,104,2.03,101,2.5
3,104,4.0
3,105,4.5
3,107,5.04,101,5.0
4,103,3.0
4,104,4.5
4,106,4.05,101,4.0
5,102,3.0
5,103,2.0
5,104,4.0
5,105,3.5
5,106,4.0用户1和用户5具有相同的喜好。他们都喜欢101这本书，对102的喜欢弱一些，对103的喜欢更弱。同理，用户1和4具有相同的兴趣，他们都喜欢101和103，没有信息显示用户4喜欢102。另一方面，用户1和用户2的兴趣好像正好相反，用户1喜欢 101，但用户2讨厌101，用户1喜欢103而用户2正好相反。用户1和3的交集很少，只有101这本书显示了他们的兴趣。
简单的推荐程序demo，如下：
package com.xh.recommender;import org.apache.mahout.cf.taste.impl.model.file.FileDataModel;
import org.apache.mahout.cf.taste.impl.neighborhood.NearestNUserNeighborhood;
import org.apache.mahout.cf.taste.impl.recommender.GenericUserBasedRecommender;
import org.apache.mahout.cf.taste.impl.similarity.PearsonCorrelationSimilarity;
import org.apache.mahout.cf.taste.model.DataModel;
import org.apache.mahout.cf.taste.neighborhood.UserNeighborhood;
import org.apache.mahout.cf.taste.recommender.RecommendedItem;
import org.apache.mahout.cf.taste.recommender.Recommender;
import org.apache.mahout.cf.taste.similarity.UserSimilarity;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import java.io.File;
import java.net.URL;
import java.util.List;/*** @author xiaohe* @version V1.0.0* @Description: mahout 推荐简介* @date: 2018-8-20 20:51* @Copyright: */
public class RecommenderIntro {private static Logger logger = LoggerFactory.getLogger(RecommenderIntro.class);public static void main(String[] args) throws Exception {final String filePath = "recommend/intro.csv";URL url = RecommenderIntro.class.getClassLoader().getResource(filePath);File modelFile = new File(url.getFile());if(!modelFile.exists()) {System.err.println("Please, specify name of file, or put file 'input.csv' into current directory!");System.exit(1);}/**** 装载 数据 文件* DataModel 实现储存并为计算机提供所需的所有偏好、用户和物品数据**/DataModel model = new FileDataModel(modelFile);/*** UserSimilarity 实现给出两个用户之间的相似度* 可以从多种可能度量或计算机中选一种作为依赖*/UserSimilarity similarity = new PearsonCorrelationSimilarity(model);// UserNeighborhood 实现 明确与给定用户最相似的一组用户UserNeighborhood neighborhood =new NearestNUserNeighborhood(2, similarity, model);/**** 生成推荐引擎* Recommender 合并所有的组件为用户推荐物品**/Recommender recommender = new GenericUserBasedRecommender(model, neighborhood, similarity);// 为用户1 推荐2件 物品List<RecommendedItem> recommendations =recommender.recommend(1, 2);for (RecommendedItem recommendation : recommendations) {System.out.println(recommendation);}}}项目结构如图：
附上pom.xml
<?xml version="1.0" encoding="UTF-8"?><project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.xh</groupId><artifactId>springboot-mahout</artifactId><version>1.0.0-SNAPSHOT</version><packaging>war</packaging><name>springboot-mahout Maven Webapp</name><!-- FIXME change it to the project's website --><url>http://www.example.com</url><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><maven.compiler.source>1.8</maven.compiler.source><maven.compiler.target>1.8</maven.compiler.target></properties><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>1.5.8.RELEASE</version><relativePath /> <!-- lookup parent from repository --></parent><dependencies><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-annotations</artifactId></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId></dependency><!-- https://mvnrepository.com/artifact/org.apache.mahout/mahout-core --><dependency><groupId>org.apache.mahout</groupId><artifactId>mahout-core</artifactId><version>0.9</version></dependency><!-- https://mvnrepository.com/artifact/commons-io/commons-io --><dependency><groupId>commons-io</groupId><artifactId>commons-io</artifactId><version>2.6</version></dependency></dependencies><build><finalName>springboot-mahout</finalName></build>
</project>