java 协同过滤算法_Mahout实现基于用户的协同过滤算法

packagecom.mahout.helloworlddemo;importjava.sql.Connection;importjava.sql.DatabaseMetaData;importjava.sql.ResultSet;importjava.sql.SQLException;importjava.sql.Statement;importjava.util.HashSet;importjava.util.List;importorg.apache.mahout.cf.taste.impl.model.jdbc.MySQLJDBCDataModel;importorg.apache.mahout.cf.taste.impl.neighborhood.NearestNUserNeighborhood;importorg.apache.mahout.cf.taste.impl.recommender.GenericUserBasedRecommender;importorg.apache.mahout.cf.taste.impl.similarity.PearsonCorrelationSimilarity;importorg.apache.mahout.cf.taste.model.DataModel;importorg.apache.mahout.cf.taste.model.JDBCDataModel;importorg.apache.mahout.cf.taste.neighborhood.UserNeighborhood;importorg.apache.mahout.cf.taste.recommender.RecommendedItem;importorg.apache.mahout.cf.taste.recommender.Recommender;importorg.apache.mahout.cf.taste.similarity.UserSimilarity;importcom.mahout.util.DBUtil;importcom.mysql.jdbc.jdbc2.optional.MysqlDataSource;/***

*@authorwxisme

*@time 2015-9-13 下午6:25:26*/

public classRecommenderIntroFromMySQL {public static void main(String[] args) throwsException {//连接MySQL

MysqlDataSource dataSource = newMysqlDataSource();

dataSource.setServerName("localhost");

dataSource.setUser("root");

dataSource.setPassword("1234");

dataSource.setDatabaseName("mahoutdemo");//获取数据模型

JDBCDataModel dataModel = new MySQLJDBCDataModel(dataSource, "taste_preferences", "user_id", "item_id", "preference","time");

DataModel model=dataModel;//计算相似度

UserSimilarity similarity = newPearsonCorrelationSimilarity(model);//计算阈值

UserNeighborhood neighborhood = new NearestNUserNeighborhood(2,similarity,model);//推荐

Recommender recommender = newGenericUserBasedRecommender(model,neighborhood,similarity);

Connection con=DBUtil.getConnection();

Statement stmt=con.createStatement();//获取每个用户的推荐数据并存入数据库

for(int i=0; i<5; i++) {

List recommendations = recommender.recommend(i, 3);

String tableName= "user_" +i;for(RecommendedItem recommendation : recommendations) {//如果是第一次推荐就创建该用户的数据表

if(!doesTableExist(tableName)) {

String createSQL= "create table " +tableName+ " (item_id bigint primary key,value float);";

stmt.execute(createSQL);

}

String insertSQL= "insert into " + tableName + " values ("

+ recommendation.getItemID() + "," + recommendation.getValue() + " );";//插入用户的推荐数据

stmt.execute(insertSQL);

System.out.println(recommendation);

}

}

}/*** 是否存在这个数据表

*@paramtablename

*@return*@throwsSQLException*/

public static Boolean doesTableExist(String tablename) throwsSQLException {

HashSet set = new HashSet();

Connection con=DBUtil.getConnection();

DatabaseMetaData meta=con.getMetaData();

ResultSet res= meta.getTables(null, null, null,new String[]{"TABLE"});while(res.next()) {

set.add(res.getString("TABLE_NAME"));

}

DBUtil.close(res, con);returnset.contains(tablename);

}

}