一步一步跟我学习lucene（10）---lucene搜索之联想词提示之suggest原理和应用

昨天了解了suggest包中的spell相关的内容，主要是拼写检查和相似度查询提示；

今天准备了解下关于联想词的内容，lucene的联想词是在org.apache.lucene.search.suggest包下边，提供了自动补全或者联想提示功能的支持；

InputIterator说明

InputIterator是一个支持枚举term,weight,payload三元组的供suggester使用的接口，目前仅支持AnalyzingSuggester,FuzzySuggester andAnalyzingInfixSuggester 三种suggester支持payloads；

InputIterator的实现类有以下几种：

BufferedInputIterator：对二进制类型的输入进行轮询；

DocumentInputIterator：从索引中被store的field中轮询；

FileIterator：从文件中每次读出单行的数据轮询，以\t进行间隔（且\t的个数最多为2个）；

HighFrequencyIterator：从索引中被store的field轮询，忽略长度小于设定值的文本；

InputIteratorWrapper：遍历BytesRefIterator并且返回的内容不包含payload且weight均为1；

SortedInputIterator：二进制类型的输入轮询且按照指定的comparator算法进行排序；

InputIterator提供的方法如下：

weight():此方法设置某个term的权重，设置的越高suggest的优先级越高；

payload():每个suggestion对应的元数据的二进制表示，我们在传输对象的时候需要转换对象或对象的某个属性为BytesRef类型，相应的suggester调用lookup的时候会返回payloads信息；

hasPayload()：判断iterator是否有payloads；

contexts():获取某个term的contexts,用来过滤suggest的内容，如果suggest的列表为空，返回null

hasContexts():获取iterator是否有contexts;

Suggester查询工具Lookup类说明

此类提供了字符串的联想查询功能

Lookup类提供了一个CharSequenceComparator，此comparator主要是用来对CharSequence进行排序，按字符顺序排序；

内置LookupResult，用于返回suggest的结果，同时也是按照CharSequenceComparator进行key的排序；

内置了LookupPriorityQueue，用以存储LookupResult;

LookUp提供的方法

build(Dictionary dict)  ： 从指定directory进行build;

load(InputStream input) ： 将InputStream转成DataInput并执行load(DataInput)方法；

store(OutputStream output) ： 将OutputStream转成DataOutput并执行store(DataOutput)方法；

getCount() ： 获取lookup的build的项的数量；

build(InputIterator inputIterator) ： 根据指定的InputIterator构建Lookup对象；

lookup(CharSequence key, boolean onlyMorePopular, int num) ：根据key查询可能的结果返回值为List<LookupResult>;

Lookup的相关实现如下：

编写自己的suggest模块

注意：在suggest的时候我们需要导入lucene-misc-5.1.0.jar否则系统会提示类SortedMergePolicy没有找到；

首先我们定义自己的实体类：

package com.lucene.suggest;

import java.io.Serializable;

public class Product implements Serializable {
    private static final long serialVersionUID = 1L;
    private String name;
    private String image;
    private String[] regions;
    private int numberSold;

    public Product(String name, String image, String[] regions, int numberSold) {
        this.name = name;
        this.image = image;
        this.regions = regions;
        this.numberSold = numberSold;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getImage() {
        return image;
    }

    public void setImage(String image) {
        this.image = image;
    }

    public String[] getRegions() {
        return regions;
    }

    public void setRegions(String[] regions) {
        this.regions = regions;
    }

    public int getNumberSold() {
        return numberSold;
    }

    public void setNumberSold(int numberSold) {
        this.numberSold = numberSold;
    }
}

然后定义InputIterator这里定义消费者是List<Object>，并对list进行遍历放入payload中：

package com.lucene.suggest;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.UnsupportedEncodingException;
import java.util.Comparator;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import org.apache.lucene.search.suggest.InputIterator;
import org.apache.lucene.util.BytesRef;

public class ProductIterator implements InputIterator {
    private Iterator<Product> productIterator;
    private Product currentProduct;

    ProductIterator(Iterator<Product> productIterator) {
        this.productIterator = productIterator;
    }

    public boolean hasContexts() {
        return true;
    }

    /**
     * 是否有设置payload信息
     */
    public boolean hasPayloads() {
        return true;
    }

    public Comparator<BytesRef> getComparator() {
        return null;
    }

    public BytesRef next() {
        if (productIterator.hasNext()) {
            currentProduct = productIterator.next();
            try {
                return new BytesRef(currentProduct.getName().getBytes("UTF8"));
            } catch (UnsupportedEncodingException e) {
                throw new RuntimeException("Couldn't convert to UTF-8",e);
            }
        } else {
            return null;
        }
    }

    public BytesRef payload() {
        try {
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            ObjectOutputStream out = new ObjectOutputStream(bos);
            out.writeObject(currentProduct);
            out.close();
            return new BytesRef(bos.toByteArray());
        } catch (IOException e) {
            throw new RuntimeException("Well that's unfortunate.");
        }
    }
    public Set<BytesRef> contexts() {
        try {
            Set<BytesRef> regions = new HashSet<BytesRef>();
            for (String region : currentProduct.getRegions()) {
                regions.add(new BytesRef(region.getBytes("UTF8")));
            }
            return regions;
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException("Couldn't convert to UTF-8");
        }
    }


    public long weight() {
        return currentProduct.getNumberSold();
    }
}

编写测试类

package com.lucene.suggest;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.search.suggest.Lookup.LookupResult;
import org.apache.lucene.search.suggest.analyzing.AnalyzingInfixSuggester;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.BytesRef;

public class SuggestProducts {
    private static void lookup(AnalyzingInfixSuggester suggester, String name,
            String region) throws IOException {
        HashSet<BytesRef> contexts = new HashSet<BytesRef>();
        contexts.add(new BytesRef(region.getBytes("UTF8")));
        List<LookupResult> results = suggester.lookup(name, contexts, 2, true, false);
        System.out.println("-- \"" + name + "\" (" + region + "):");
        for (LookupResult result : results) {
            System.out.println(result.key);
            BytesRef bytesRef = result.payload;
            ObjectInputStream is = new ObjectInputStream(new ByteArrayInputStream(bytesRef.bytes));
            Product product = null;
            try {
                product = (Product)is.readObject();
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            System.out.println("product-Name:" + product.getName());
            System.out.println("product-regions:" + product.getRegions());
            System.out.println("product-image:" + product.getImage());
            System.out.println("product-numberSold:" + product.getNumberSold());
        }
        System.out.println();
    }

    public static void main(String[] args) {
        try {
            Directory indexDir = FSDirectory.open(Paths.get("suggestPath", new String[0]));
            StandardAnalyzer analyzer = new StandardAnalyzer();
            AnalyzingInfixSuggester suggester = new AnalyzingInfixSuggester(indexDir, analyzer);
            ArrayList<Product> products = new ArrayList<Product>();
            products.add(new Product("Electric Guitar",
                    "http://images.example/electric-guitar.jpg", new String[] {
                            "US", "CA" }, 100));
            products.add(new Product("Electric Train",
                    "http://images.example/train.jpg", new String[] { "US",
                            "CA" }, 100));
            products.add(new Product("Acoustic Guitar",
                    "http://images.example/acoustic-guitar.jpg", new String[] {
                            "US", "ZA" }, 80));
            products.add(new Product("Guarana Soda",
                    "http://images.example/soda.jpg",
                    new String[] { "ZA", "IE" }, 130));

            suggester.build(new ProductIterator(products.iterator()));

            lookup(suggester, "Gu", "US");
            lookup(suggester, "Gu", "ZA");
            lookup(suggester, "Gui", "CA");
            lookup(suggester, "Electric guit", "US");
            suggester.refresh();
        } catch (IOException e) {
            System.err.println("Error!");
        }
    }
}