除了内容,Tika还从文件中提取元数据.元数据只不过是随文件提供的附加信息.如果我们考虑音频文件,则艺术家名称,专辑名称,标题属于元数据.
XMP标准
可扩展元数据平台(XMP)是用于处理和存储与文件内容相关的信息的标准.它由 Adobe Systems Inc 创建. XMP提供了用于定义,创建和处理元数据的标准.您可以将此标准嵌入到多种文件格式中,例如 PDF , JPEG , JPEG , GIF , jpg , HTML 等.
属性类
Tika使用Property类来跟踪XMP属性定义.它提供 PropertyType 和 ValueType 枚举以捕获元数据的名称和值.
元数据类
此类实现各种接口,例如 ClimateForcast , CativeCommons,地理,TIFF等,为各种元数据模型提供支持.此外,此类提供了从文件中提取内容的各种方法.
元数据名称
我们可以提取所有元数据名称的列表使用 names()方法从其元数据对象中获取文件.它将所有名称作为字符串数组返回.使用元数据的名称,我们可以使用 get()方法获取值.它采用元数据名称并返回与之关联的值.
String[] metadaNames = metadata.names();String value = metadata.get(name);
使用解析方法提取元数据
每当我们使用parse()解析文件时,我们都会传递一个空的元数据对象作为参数之一.此方法提取给定文件的元数据(如果该文件包含任何文件),并将它们放在元数据对象中.因此,在使用parse()解析文件后,我们可以从该对象中提取元数据.
Parser parser = new AutoDetectParser();BodyContentHandler handler = new BodyContentHandler();Metadata metadata = new Metadata(); //empty metadata object FileInputStream inputstream = new FileInputStream(file);ParseContext context = new ParseContext();parser.parse(inputstream, handler, metadata, context);// now this metadata object contains the extracted metadata of the given file.metadata.metadata.names();
以下是从文本文件中提取元数据的完整程序.
import java.io.File;import java.io.FileInputStream;import java.io.IOException;import org.apache.tika.exception.TikaException;import org.apache.tika.metadata.Metadata;import org.apache.tika.parser.AutoDetectParser;import org.apache.tika.parser.ParseContext;import org.apache.tika.parser.Parser;import org.apache.tika.sax.BodyContentHandler;import org.xml.sax.SAXException;public class GetMetadata { public static void main(final String[] args) throws IOException, TikaException { //Assume that boy.jpg is in your current directory File file = new File("boy.jpg"); //Parser method parameters Parser parser = new AutoDetectParser(); BodyContentHandler handler = new BodyContentHandler(); Metadata metadata = new Metadata(); FileInputStream inputstream = new FileInputStream(file); ParseContext context = new ParseContext(); parser.parse(inputstream, handler, metadata, context); System.out.println(handler.toString()); //getting the list of all meta data elements String[] metadataNames = metadata.names(); for(String name : metadataNames) { System.out.println(name + ": " + metadata.get(name)); } }}
将上述代码保存为GetMetadata.java并使用命令提示符从命令提示符运行以下命令 :
javac GetMetadata .javajava GetMetadata
以下是boy.jpg的快照
如果你执行上面的程序,它会给你以下输出 :
X-Parsed-By: org.apache.tika.parser.DefaultParserResolution Units: inchCompression Type: BaselineData Precision: 8 bitsNumber of Components: 3tiff:ImageLength: 3000Component 2: Cb component: Quantization table 1, Sampling factors 1 horiz/1 vertComponent 1: Y component: Quantization table 0, Sampling factors 2 horiz/2 vertImage Height: 3000 pixelsX Resolution: 300 dotsOriginal Transmission Reference: 53616c7465645f5f2368da84ca932841b336ac1a49edb1a93fae938b8db2cb3ec9cc4dc28d7383f1Image Width: 4000 pixelsIPTC-NAA record: 92 bytes binary dataComponent 3: Cr component: Quantization table 1, Sampling factors 1 horiz/1 verttiff:BitsPerSample: 8Application Record Version: 4tiff:ImageWidth: 4000Content-Type: image/jpegY Resolution: 300 dots
我们还可以获得所需的元数据值.
添加新的元数据值
我们可以添加新的元数据值使用元数据类的add()方法.下面给出了此方法的语法.这里我们添加作者姓名.
metadata.add("author","Tutorials point");
元数据类具有预定义的属性,包括从 ClimateForcast ,CativeCommons,地理等,以支持各种数据模型.下面显示的是使用从Tika实现的TIFF接口继承的SOFTWARE数据类型,以遵循TIFF图像格式的XMP元数据标准.
metadata .add(Metadata.SOFTWARE,"ms paint");
以下是演示如何将元数据值添加到给定文件的完整程序.这里元数据元素的列表显示在输出中,以便您可以在添加新值后观察列表中的更改.
import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.util.Arrays;import org.apache.tika.exception.TikaException;import org.apache.tika.metadata.Metadata;import org.apache.tika.parser.AutoDetectParser;import org.apache.tika.parser.ParseContext;import org.apache.tika.parser.Parser;import org.apache.tika.sax.BodyContentHandler;import org.xml.sax.SAXException;public class AddMetadata { public static void main(final String[] args) throws IOException, SAXException, TikaException { //create a file object and assume sample.txt is in your current directory File file = new File("Example.txt"); //Parser method parameters Parser parser = new AutoDetectParser(); BodyContentHandler handler = new BodyContentHandler(); Metadata metadata = new Metadata(); FileInputStream inputstream = new FileInputStream(file); ParseContext context = new ParseContext(); //parsing the document parser.parse(inputstream, handler, metadata, context); //list of meta data elements before adding new elements System.out.println( " metadata elements :" +Arrays.toString(metadata.names())); //adding new meta data name value pair metadata.add("Author","Tutorials Point"); System.out.println(" metadata name value pair is successfully added"); //printing all the meta data elements after adding new elements System.out.println("Here is the list of all the metadata elements after adding new elements"); System.out.println( Arrays.toString(metadata.names())); }}
将上面的代码保存为AddMetadata.java类并从命令提示符运行它 :
javac AddMetadata .java java AddMetadata
以下是内容of Example.txt
Hi students welcome to IT屋
如果你执行上面的程序,它会给你以下输出 :
metadata elements of the given file :[Content-Encoding, Content-Type] enter the number of metadata name value pairs to be added 1enter metadata1name: Author enter metadata1value: Tutorials point metadata name value pair is successfully addedHere is the list of all the metadata elements after adding new elements[Content-Encoding, Author, Content-Type]
将值设置为现有元数据元素
您可以使用set()方法将值设置为现有元数据元素.使用set()方法设置date属性的语法如下 :
metadata.set(Metadata.DATE, new Date());
您还可以使用set()方法为属性设置多个值.使用set()方法为Author属性设置多个值的语法如下 :
metadata.set(Metadata.AUTHOR, "ram ,raheem ,robin ");
以下是演示set()方法的完整程序.
import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.util.Date;import org.apache.tika.exception.TikaException;import org.apache.tika.metadata.Metadata;import org.apache.tika.parser.AutoDetectParser;import org.apache.tika.parser.ParseContext;import org.apache.tika.parser.Parser;import org.apache.tika.sax.BodyContentHandler;import org.xml.sax.SAXException;public class SetMetadata { public static void main(final String[] args) throws IOException,SAXException, TikaException { //Create a file object and assume example.txt is in your current directory File file = new File("example.txt"); //parameters of parse() method Parser parser = new AutoDetectParser(); BodyContentHandler handler = new BodyContentHandler(); Metadata metadata = new Metadata(); FileInputStream inputstream = new FileInputStream(file); ParseContext context = new ParseContext(); //Parsing the given file parser.parse(inputstream, handler, metadata, context); //list of meta data elements elements System.out.println( " metadata elements and values of the given file :"); String[] metadataNamesb4 = metadata.names(); for(String name : metadataNamesb4) { System.out.println(name + ": " + metadata.get(name)); } //setting date meta data metadata.set(Metadata.DATE, new Date()); //setting multiple values to author property metadata.set(Metadata.AUTHOR, "ram ,raheem ,robin "); //printing all the meta data elements with new elements System.out.println("List of all the metadata elements after adding new elements "); String[] metadataNamesafter = metadata.names(); for(String name : metadataNamesafter) { System.out.println(name + ": " + metadata.get(name)); } }}
将上述代码保存为SetMetadata.java并从命令提示符 : 运行它;
javac SetMetadata.java java SetMetadata
给定以下是example.txt的内容.
Hi students welcome to IT屋
如果执行上述程序,它将为您提供以下输出.在输出中,您可以观察新添加的元数据元素.
metadata elements and values of the given file :Content-Encoding: ISO-8859-1Content-Type: text/plain; charset = ISO-8859-1Here is the list of all the metadata elements after adding new elements date: 2014-09-24T07:01:32ZContent-Encoding: ISO-8859-1Author: ram, raheem, robin Content-Type: text/plain; charset = ISO-8859-1