Lucene 深入学习（3）Lucene索引初识

野性酷女 2022-06-06 00:08 264阅读 0赞

**前言：** Lucene的倒排索引是了解整个搜索的入口，本节将通过代码实例的方式初步认识Lucene的索引创建过程。

## 原始文档 ##

可以使用任何文本文件来熟悉Lucene索引的创建，这里我选用了经典作品《致加西亚的信》英文版 A Message to Garcia，你可以在互联网上轻易地找到这篇文章。之所以用英文材料，是因为Lucene默认只支持英文，英文材料可以避免出现分词不准确造成的认知偏差，在学习完分词的相关知识后，会采用中文演示案例。

## 代码实例 ##

Lucene是用Java语言实现的，可以很方便使用Java语言对其扩展。不过在Lucene开源以后，已经有了其他语言的实现版本。

public void index(){
            //使用了标准分词器，可以选择的分词很多
            Analyzer analyzer = new StandardAnalyzer();
            //可以先将索引存储在内存中
            Directory directory = new RAMDirectory();
    
            IndexWriterConfig config = new IndexWriterConfig(analyzer);
            IndexWriter writer = null;
            try {
                writer = new IndexWriter(directory, config);
                //选择了一些片段
                String[] texts = new String[]{
                        "In all this Cuban business there is one man stands out on the horizon of my memory like Mars at perihelion.",
                        "Garcia was somewhere in the mountain vastness of Cuba- no one knew where.",
                        "Some one said to the President, There’s a fellow by the name of Rowan will find Garcia for you, if anybody can.",
                        "Rowan was sent for and given a letter to be delivered to Garcia.",
                        "The point I wish to make is this: McKinley gave Rowan a letter to be delivered to Garcia;",
                        "General Garcia is dead now, but there are other Garcias.",
                        "He will look at you out of a fishy eye and ask one or more of the following questions",
                        "What do you want to know for?",
                        "Can such a one write a letter to Garcia?",
                        "Can such a man be entrusted to carry a message to Garcia?"
                    };
    
                    for (String text : texts) {
                        Document doc = new Document();
                        doc.add(new Field("fieldname", text, TextField.TYPE_STORED));
                        writer.addDocument(doc);
                    }
                    writer.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

很简单的实例来演示了Lucene创建索引的过程，简单的总结一下，应该按下面的步骤创建Luncene索引：  
1. 指定分词策略（选分词器Analyzer）;  
2. 通过添加字段(Field)创建文档(Document)；  
3. 创建IndexWriter，通过addDocument()方法添加文档(Document)