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J2EE and The Next Generation

J2EE and The Next Generation. 内容列表. 1 XML and J2EE 1.3 2 Web Service and J2EE 1.5 3 Java EE 5.0 4 J2EE vs .NET 5 小结. 1 XML & J2EE 1.3. XML DTD, Schema XML Parser J2EE 1.3. [01] <?XML version="1.0" standalone="yes"?> [11] <Students Class=”SY9061”> [12] <Student SId="12345">

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J2EE and The Next Generation

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  1. J2EE and The Next Generation

  2. 内容列表 • 1 XML and J2EE 1.3 • 2 Web Service and J2EE 1.5 • 3 Java EE 5.0 • 4 J2EE vs .NET • 5 小结

  3. 1 XML & J2EE 1.3 • XML • DTD, Schema • XML Parser • J2EE 1.3

  4. [01] <?XML version="1.0" standalone="yes"?> [11] <Students Class=”SY9061”> [12] <Student SId="12345"> [13] <Name>Lin</Name> [14] <Age>20</Age> [15] </Student> [16] <Student SId="12345"> [17] <Name>Lin</Name> [18] </Student> [19] </Students>

  5. What Is XML? • XML was developed by an XML Working Group of the World Wide Web Consortium (W3C) in 1996 • It was chaired by Jon Bosak of Sun Microsystems • XML is a family of technologies: XSL, XSLT, XPath, Xlink, Xpointer, DOM, etc. • XML is license-free, platform-independent and well-supported

  6. The eXtensible Markup Language (XML) is the universal format for structured documents and data on the Web • As with HTML, you identify data using tags (identifiers enclosed in angle brackets, like this: <...>) • The tags are called "markup" • But unlike HTML, XML tags tell you what the data means, rather than how to display it

  7. XML Document • A data object is an XML document if it is well-formed, as defined in XML specification • A well-formed XML document may in addition be valid if it meets certain further constraints • The document is composed of declarations, elements, comments, character references, and processing instructions, all of which are indicated in the document by explicit markup

  8. Well-Formed XML Documents • A "Well Formed" XML document has correct XML syntax • A textual object is a well-formed XML document if it has the correct XML syntax: • It contains one or more elements • There is exactly one element, called the root, or document element • The name in an element's end-tag must match the element type in the start-tag; Names are case-sensitive • Each of the parsed entities which is referenced directly or indirectly within the document is well-formed

  9. XML Document Contents • Processing Instructions • XML declaration • Elements • Tags: Start-Tags, End-Tags • Attributes • Empty-Element Tags • PCDATA • CDATA • White Spaces • Comments Prolog Content

  10. 序言 • XML声明: • XML文档应该以XML声明作为文档的开始,声明中指定了版本、编码等信息 • 文档类型声明: • DOCTYPE声明必须位于XML声明之后,且在任何文档元素之前。但是,XML声明和DOCTYPE声明之间可以插入注释和处理指令。 • 混合项 • 注释 • 处理指令 • 空白字符

  11. 主体 • XML文档的主体是文档元素,每个XML文档都有且仅有一个文档元素,文档元素可以包含子元素(多个)。

  12. 尾声 • 包括注释、处理指令、与/或空白 ,即序言中的混合项

  13. An Example XML Document • <?xml version="1.0" encoding="ISO-8859-1"?> • <tradeBatch> • <trade account="2520034" action="buy" Duration = "good-till-canceled"> • <symbol>SUNW</symbol> • <quantity>1000</quantity> • <limit>20</limit> • <date>2001-03-05</date> • </trade> • <trade account="9240196" action="sell" duration="day"> • <symbol>CSCO</symbol> • <quantity>500</quantity> • <date>2001-03-05</date> • </trade> • </tradeBatch> • <!-- This is a comment -->

  14. 有效的文档 • 有效的文档: • 格式良好 • 包含文档类型声明 • 文档实例符合文档类型声明的约束。有效的文档: • 有效性约束的两种方法: • DTD • Schema

  15. DTD • 文档类型定义(Document Type Definition ,DTD)是XML 1.0规范的一部分 • DTD可以定义词汇和词汇之间的语法规则,从而定义XML文档的结构。

  16. 1: <?XML version="1.0" standalone="yes"?> 2: <!DOCTYPE Students [ 4: <!ELEMENT Students (Student+)> 5: <!ATTLIST Students Class CDATA #REQUIRED> 6: <!ELEMENT Student (Name, Age?)> 7: <!ATTLIST Student SId CDATA #REQUIRED> 9: <!ELEMENT Name (#PCDATA)> 13: <!ELEMENT Age (#PCDATA)> 18: ]> 19: <Students Class=”SY9061”> 20: <Student SId="12345"> 21: <Name>Lin</Name> 22: <Age>20</Age> 23: <Address> 24: <Country>China</Country> 25: <City>BeiJing</City> 26: </Address> 27: </Student> 28: <Student SId="12345"> 29: <Name>Lin</Name> 30: </Student> 31: </Students>

  17. DTD各要素 • ELEMENT –元素 • 元素类型声明 • ATTLIST • 特定元素类型可设置的属性及这些属性的允许值声明 • ENTITY • 可重用的内容声明 • NOTATION • 不需要解析的外部内容(例如:二进制数据)的格式声明,以及用于处理这些内容的外部应用程序

  18. DTD与文档的关联 • DOCTYPE 标记 • 内部DTD子集 • <!DocType catalog[… 内部声明 …]> • 外部DTD子集 • <!DOCTYPE catalog SYSTEM “http://myserver/decs/pubcatalog.dtd”>

  19. 有效性验证 • 利用D T D 和验证有效性的解析器,就能够立即对文档的完整性进行可靠的检查 。如果某个X M L 文档引用了D T D ,验证有效性的解析器应该读取D T D ,并确保文档符合D T D 中描述的语法

  20. DTD的缺点 • DTD有自己的特殊的语法,本身不是XML文档因此,我们编写XML文档时,需要使用两套解析器:一套用来分析XML,判断文档是否格式良好;另一套用于分析DTD,再用分析的结果去检查XML文档,判断XML是否有效。 • DTD只提供了有限的数据类型 • 结构封闭,不具备扩展性。DTD不支持名域机制,因此,每个XML文档只能有一个DTD,从而限制了XML文档的继承和重用。

  21. 2: <!DOCTYPE Students [ 4: <!ELEMENT Students (Student+)> 5: <!ATTLIST Students Class CDATA #REQUIRED> 6: <!ELEMENT Student (Name, Age?)> 7: <!ATTLIST Student SId CDATA #REQUIRED> 9: <!ELEMENT Name (#PCDATA)> 13: <!ELEMENT Age (#PCDATA)> 18: ]> !定义元素和内容模型 1: <?XML version="1.0" standalone="yes"?> 19: <Students Class=”SY9061”> 20: <Student SId="12345"> 21: <Name>Lin</Name> 22: <Age>20</Age> 23: <Address> 24: <Country>China</Country> 25: <City>BeiJing</City> 26: </Address> 27: </Student> 28: <Student SId="12345"> 29: <Name>Lin</Name> 30: </Student> 31: </Students>

  22. [01]<xsd:schema xmlns:xsd=http://www.w3.org/2000/08/XMLSchema [02] targetNamespace=”http://cscw.buaa.edu.cn/Schema-Stud”> [03] <xsd:element name="students" type="StudentsType"/> [09] <xsd:complexType name="StudentsType"> [10] <xsd:sequence> [11] <xsd:element name="student" type="StudentType" maxOccus=”unbounded”/> [12] </xsd:sequence> [13] <xsd:attribute name="class" type="xsd:NMTOKEN"/> [14] </xsd:complexType> [15] <xsd:complexType name="StudentType"> [16] <xsd:sequence> [17] <xsd:element name="name" type="xsd:string"/> [18] <xsd:element name="age" type="xsd:int" minOccus=”0”/> [19] </xsd:sequence> [20] <xsd:attribute name="sId" type="xsd:NMTOKEN"/> [21] </xsd:complexType> [22]</xsd:schema> !名域声明 ! 声明元素 !定义类型

  23. Schema的基本概念 • 类型定义 • 元素声明 • 名域 • ……

  24. 类型定义 <xsd:complexType name="StudentType"> <xsd:sequence> <xsd:element name="name" type="xsd:string"/> <xsd:element name="age“ type="xsd:int“ minOccus=”0”/> </xsd:sequence> <xsd:attribute name=“sId“ type="xsd:NMTOKEN"/> </xsd:complexType> Class StudentType{ String name; int age; String sid; }

  25. 元素声明 • 元素声明: <xsd:element name=“age" type=”xsd:int”/> 对应于java中的变量声明: int age; • 属性声明: <xsd:attribute name=“b" type="xsd:NMTOKEN“ use="fixed" value="US"/> 对应于Java的变量声明 NMTOKEN b;

  26. Namespace • Namespace • Schema中通过元素<schema>的属性targetNamspace指定名域: targetNamespace=“http://www.example.com/PO1” Namespace对应于Java中的package,如: package cscw.mypackage (C#没有package,改成namespace)

  27. Schema • Java程序是类的集合,Schema是类型定义和元素声明的集合 ,因此,Schema可以类比于Java程序

  28. XML文档实例 • 元素实例 • 进一步类推,可以得出XML文档的元素实例类比于Java中的类实例: • student = new StudentType(); • XML文档元素与Java类实例的类比是差别最大的类比关系:前者是静态的文档,以字符形式存在;后者是程序的动态运行,以二进制形式存在于内存中。其实这个差别正是XML得以广泛应用的原因之一:二进制的数据很难在网络的不同应用之间传递,而文本数据则很容易。 • 文档实例 • XML文档实例类比于运行中的Java程序。

  29. Schema与Java类比汇总

  30. Schema与XML文档的关联 [01]<?xml version="1.0"?> [02]<students [03] xmlns:stud=”http://act.buaa.edu.cn/Schema-Stud” [04] class=”SY9061”> [05] <student SId="12345"> [06] <name>Lin</name> [07] <age>20</age> [08] </student> [09] <student sId="345657"> [10] <name>Li</name> [11] </student> [12]</students>

  31. Schema的优点 • 本身是XML文档 • 内建丰富的数据类型;可以方便地定义数据类型 • 支持名域(namespace)

  32. XML文档的处理 • 回调 • 回调是作为一种事件驱动模型工作的。当分析 XML 文档时,某些事件将触发回调方法。 • SAX,用于 XML 的一种简单 API,是这种 XML 使用方法的事实上的标准。 • 树 • 根据XML 文档,创建对应的树状结构。 • 最流行的 API 是文档对象模型 (DOM)。 • 数据绑定 • 将XML Schema编译成一个或多个Java 类,其后,XML对象和Java对象可以相互转换。 • Sun 公司的DataBinding

  33. SAX——Simple API for XML • SAX(Simple Application interface for XML)接口规范是XML分析器和XML处理器提供的较XML更底层的接口。 • SAX诞生是在XML-DEV讨论组上,提出它的原因是有一些情况不适用DOM接口,而且DOM实现太大而且比较慢。 • SAX是一种事件驱动的接口,它的基本原理是,由接口的用户提供符合定义的处理器,XML分析时遇到特定的事件,就去调用处理器中特定事件的处理函数。一般SAX都是JAVA的接口,但其实C++也可以用SAX接口,但C++的分析器比较少。

  34. Parsing • Reading and well-formed'ness checking and validating • Event-driven Parser • You provide the event Handler • Sequential read access only => one-time access • Fast and Lightweight • Documents does not have to be entirely in memory • Does not support modification of document • Started as a Community-driven project • org.xml.sax • SAX is free!

  35. SAX Example • <?xml version="1.0"?> • <doc> • <para>Hello, world!</para> • </doc> • An event-based interface will break the structure of this document down into a series of linear events: • start document • start element: doc • start element: para • characters: Hello, world! • end element: para • end element: doc • end document

  36. SAX需要用户提供一下几个处理器类的实现: • DocumentHandlerXML:文件事件的处理器; • DTDHandler:DTD中事件的处理器; • ErrorHandler:出错处理器。 • 写程序就是以下这么几步了: • 首先需要从这几个类继承出自己的子类, • 重载其中自己感兴趣的事件的处理方法。 • 向分析器,注册此处理器类,其实告诉分析器使用你的处理器。 • 启动分析器。

  37. SAXParser parser=new SAXParser(); //注册事件处理器 parser.setDocumentHandler(new MyDocumentHandler()); parser.setErrorHandler(new MyErrorHandler()); //解析文档 try{ parser.parser(fn); }catch(Exception e){ System.out.println(“Exception invoking parser.”); }

  38. DOM: Document Object Model • The Document Object Model (DOM) is an application programming interface (API) for processing well-formed and valid XML documents • It defines the logical structure of documents and the way a document is accessed and manipulated • With the Document Object Model, programmers can build documents, navigate their structure, and add, modify, or delete elements and content

  39. DOM Example:Example table, taken from an HTML document • <TABLE> • <TBODY> • <TR> • <TD>Shady Grove</TD> • <TD>Aeolian</TD> • </TR> • <TR> • <TD>Over the River, Charlie</TD> • <TD>Dorian</TD> • </TR> • </TBODY> • </TABLE>

  40. DOM规范定义了对象和接口的集合,通过他们可以访问和操作文档对象DOM规范定义了对象和接口的集合,通过他们可以访问和操作文档对象 • DOM定义了12种节点类型,有些类型的节点有不同的子节点,另外一些节点没有再低层的子节点,所有这些节点构成了树型结构,描述了文档的逻辑结构。 • Document • Element • Attr • Text

  41. import java.xml.parsers.*; import org.w3c.dom.*; DocumentBuilderFactory factory= DocumentBuilderFactory.newInstance(); factory.setValidating(true); //构造解析器 DocumentBuilder builder = factory.newDocumnetBuilder(); //解析文档,得到文档对象 Document doc=builder.parse("mydoc.xml");

  42. JAXB • Java Architecture for XML Binding • JAXB provides a fast and convenient way to create a two-way mapping between XML documents and Java objects • WARNING: Significant changes could occur between the current working draft and the final 1.0 specification

  43. Motivations of JAXB • SAX and DOM • Too low-level APIs • Requires XML knowledge • Hard to program • You have to build your high-level Java objects yourself • Hard to maintain • Schema change forces reprogramming • Forces a lot of coding • Need for APIs that provide higher-level abstraction

  44. XML Binding——What Is It? • Map components of an XML document to in-memory objects • Object should represent intended meaning of document according to its schema • What should the classes be? • Some cases obvious: String, Date, Vector. • In general, classes should be generated directly from the schema, i.e.: • A Java. technology-level binding of the schema

  45. Schema vs. Class

  46. The Binding Framework Cycle

  47. Others • Namespace in XML • XML Information set • Canonical XML • XPath • XML Digital Signature • XML Encryption • XSL • XSLT • XPointer • XLink • XBase

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