Component Based Software Engineering

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Kory Watts
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1 Component Based Software Engineering Masato Suzuki School of Information Science Japan Advanced Institute of Science and Technology 1 Schedule Mar :30-15:00 : 09. Introduction and basic concepts 15:10-16:40 : 10. Client side components(1) Mar :30-15:00 : 11. Client side components(2) 15:10-16:40 : 12. Server side components(1) Mar :30-15:00 : 13. Server side components(2) 15:10-16:40 : 14. Frameworks and middlewares Mar :30-14:00 : 15. State-of-the-art topics 2

2 #10 Client side components(1) Contents!! Java and related technologies!! OO programming style!!information hidding!!inheritance!!delegation!! Applet and its deployment!! JavaBeans 3 Java and related technologies!! Java is a one of OOPL.!! JavaBeans is a part which provide simple functions.!! Enterprise JavaBeans is a part of service and communication required business applications. JavaSE: mainly used for client side JavaEE: mainly used for server side JavaME: used for embedding system Software Development Kit (SDK) is also included. All products are free of charge. 4

3 Java SE consists of JavaSE!! JRE (Java Runtime Environment)!! Java VM (byte code interpreter)!! Core: Util, Lang, Network, Security, XML,...!! Communication: RMI, JDBC, JNDI, CORBA I/F,...!! GUI: AWT, Swing/SWT!! Deployment: Java Web Start, Java Plug-in A compiler (javac), disassembler (javap), debugger (jdb), documentation tool (javadoc) are also provided. 5 JavaSE Overview -./0.0"1#.%)! '"#1&0.2! -.3$44.2! 5(/(-"'! 5678! -.10"G#.%)! 5(/(CA.3C>)(2)! 5(/(C60$4!H!&%! *+,! >"$%-! >?&%4@>AB! 8''.EE&3&0&)G! AWT 5(/(F7!,%1$)C#.)D"-E! >7P! 59O!!"##$%&'()&"%! 9:,! 57;!! 5<7,!!=9;8!!"2.! I:J! J"44&%4! 5(/(;.(%E! J"'(0.C>$11"2)! 62.K.2.%'.E!!"00.')&"%E! 5<,! >.'$2&)G! J(%4! +)&0! <.?C,@=! <.)?"2L&%4! 5(/(!CM:C(%-C$)&0&)G! 5(/(CN")>1")C!0&.%)C!"#1&0.2! 5(/(CN")E1")CM:C9$%)&#.! 5(/(CN")>1")C>.2/.2C!"#1&0.2! 6

4 OO Programming Style!! The world is modelled by a collection of objects.!! An object has a collection of methods!! An object has a collectuon of data, but it is only accessible from proper methods (information hiding)!! Objects which have common features might be integrated by generalization (inheritance)!! Objects have a proper responsibility when they are integrated into other objects (delegation)!! Objects are always want to integrated to higher abstract objects (polymorphism) 7 Structure in Java Program Name space!! Collection of classes which are used together!! NS are separated by. hierarchically!! import is required before using another NS java lang awt String Graphics import java.*; import java.lang.*; import java.awt.*; public void paint(graphics g) { String s = new String( Hello ); Caution: this is a different concept from inheritance! 8

5 Information Hiding!! Object may contains data.!! Data can be accessed only from some specified methods. java.awt.rectangle??? +inside(x,y): bool +intersection(x3,y3,x4,y4) +move(x,y)... +Rectangle(x,y,w,h) (x1,y1) (x2,y2) is (x,y) inside of rect? extract common area move initialize (x1,y1) h w 9 Information hiding with packages Scope of methods/vars are defined as followsq!! public: from all classes in all packages!! (default): from all classes in the same package!! private: from the only classes which is defined mypack package mypack; package mypack; public class App1() { private int v11; void m11() {... private void m12() {... class App13() {... public class App2() { public int v21; void m21() {... private void m22() {... class App23() {... 10

6 Inheritance!! A mechanism in order to integrated objects which have some common features.!! Extract common to the superclass.!! Specific features are defined in the class. java.applet.applet required for ALL applets +getparameter() MyApplet +paint() specified to THIS applet void paint(graphics gc) { String m; m = getparameter( message ); gc.drawstring(m, 100, 100); 11 Delegation!! Operation which requests to another object for executing some paticular operation.!! Object must have assocication to the target of delegation OKButton OKCommand 10/20 10/22 s:1 t:2 OK NO MyApplet -OKbutton -NObutton +MyApplet() Caution: performance is out of the sight. NOButton +actionperformed(e) db.submit(r) MyApplet() { JButton b = new OKButton(); ActionListener l=new OKCommand() b.addactionlistener(l); 12

7 Interface and implementation(1)!! interface is defined as a class who has public methods only!! A class which implements an interface is considered as if it were a type of the interface. ActionListener MyCommand actionp actionp interface ActionListener { public void actionperformed(e); ; public class MyCommand implements ActionListener { public void actionperformed(actionevent e) { // operation ; 13 Interface and implementation(2)!! Multiple inheritance is realized by a class in which multiple interfaces are implemented. ActionListener actionp actionp readobj writeobj MyApp If you implement an I/F, it has the same effect to inherit the specified class. Serializable readobj writeobj class MyApp implements ActionListener, Serializable { public void actionperformed(actionevent e) {... public void writeobject(objectoutputstream out) {... public void readobject(objectinputstream in) {... ; All classes which have ActionListener can receive the events. All classes which have Serializable can suspend/resume their status. 14

8 Application and Applet Toplevel classes are different.!! Application is build by extending javax.swing.jframe.!! Applet is build by extending javax.swing.japplet. Stand-alone application JVM Swing JFrame ActionEvent MyFrame MyPane MyField Runs independently on JVM. Responsible to all operation incl. resize/scroll etc. Applet JVM WEB Browser Frame JApplet Text Form MyApplet An extention of WEB browser. Runs under control of WEB Browser. Only responsible to its contents. Applets are preferred for developers. 15 Deployment of Application Java archive (jar) file is a unit of deployment. % jar cfm app.jar MANIFEST.MF mypack/* app.jar another host (any) app.jar MANIFEST.MF Manifest Version:1.0 Main-Class: mypack.myapp deploy entry (project) package mypack; public class MyApp() { public MyApp() {... public main(...) {... developer's host MyApp.class mypack C1.class C2.class package mypack; public class C1() { package mypack; public class C2() { % java -jar -classpath any app.jar Manual operations (eg. copying jar files) are required. 16

9 Running Applets on Browser We need a HTML file which specifies name, size, of applets as well as the jar file. When the browser read it, applets are deployed (downloaded) automatically. Hello entry download MyApplet.html <html> <body> <object... classid="java:myapplet" archive="app.jar" width="200" height="150"> <param name="message value="hello"> </object> </body> </html> app.jar MyApplet.class Java VM on which WEB browser run MyApplet.class 17 JavaBeans It is a component system for building clients in Java.!! Each components are called Bean.!! Contents!! General purpose logic parts ( may contains graphics )!! Visual programming!! Supports by IDE!! Jbuilder (Borland)!! Eclipse (IBM => eclipse.org)!! NetBeans (Sun MicroSystems)!! Features!! Introspection!! Serialization!! Jar files are used for packaging and deployment. 18

10 JavaBeans Architecture!! Place reusable GUI parts into a platform.!! Each parts has their specified visuals.!! All parts are running on the same JVM process. Application an adapter Bean Bean Bean Bean SDK or IDE(eg. Eclipse) JavaBeans API, Events introspection serialization JVM 19 Definition of Bean!! It must have a default constructor.!! It must implement java.io.serializable by itself, or inherits a class which implements that interface.!! It may have a meta-infomation called BeanInfo. java.beans.beans is a collection of utility classes. IDE will help us to develop many cases. 20

11 Introspection Structure of a Bean and corresponding BeanInfo MyBean MyBeanInfo properties and accessors public methods events event lister event functions private String foo; setfoo(string f); String getfoo(); public void func(); class BaaEvent { ; interface BaaLister; void AddBaaLister(); void removebaalister(); property descrpter method descripter eventset descripter Bean and BeanInfo are usually packed into the same jar. 21 Serialization A mechanism for suspend/resume its status MyBean foo Hello baa 3 MyBean foo Hello writeobject(out) readobject(in) public class MyBean implements Serializable { private String foo; static int baa; public writeobject(objectoutputstream out) { out.defaultwrite(); out.writeint(baa); public readobject(objectinputstream in) { in.defaultread(); MyBean.baa = in.readint(); 22

12 Summary!! Basic structure of Java programs!! Packages define the visibility of classes/methods/vars.!! Interface is a mechanism which makes extension of classes easily by implemeting the methods.!! Application and Applet!! Toplevel classes are different.!! Initialization process are almost same.!! Applet is only responsible for its contents.!! Applet is automatically deployed.!! JavaBeans!! Introspection supports indirect invocation.!! Serialization supports suspend/resume of enactment. 23 Next Chapter Client side components (2)!! JavaBeans!! Deligation event model!! Indirect connection by adapters!! MVC architecture style!! Examples 24

13 Exercise Review the content of my lecture by answering the following simple questions.!! What is the JavaSE / JavaEE?!! What is a namespace?!! What is an applet?!! What is the difference between applets and stand-alone applications?!! Why applets are preferred to applications?!! What is a JavaBean?!! What is the introspection?!! What is the serialization? 25

Outline. Introduction to Java. What Is Java? History. Java 2 Platform. Java 2 Platform Standard Edition. Introduction Java 2 Platform

Outline. Introduction to Java. What Is Java? History. Java 2 Platform. Java 2 Platform Standard Edition. Introduction Java 2 Platform Outline Introduction to Java Introduction Java 2 Platform CS 3300 Object-Oriented Concepts Introduction to Java 2 What Is Java? History Characteristics of Java History James Gosling at Sun Microsystems