JAVA? Millest räägime. Servlet, JSP. Hello World JAVA. JAVA - Versions. JAVA - primary goals. JAVA Web Container Servlet JSP

Transcription

1 Millest räägime Servlet, JSP Margus Hanni, Nortal AS JAVA Web Container Servlet JSP Hello World JAVA 1 2 #include <stdio.h> int main() { printf("hello World\n"); return 0; 3 4 public class HelloWorld { public static void main(string[] args) { System.out.println("Hello, World"); <? echo 'hello World';?> <%= new String("Hello!") %> JAVA? JAVA - primary goals JAVA - Versions Five primary goals in the creation of the Java language: 1. It should use the object-oriented programming methodology. 2. It should allow the same program to be executed on multiple operating systems. 3. It should contain built-in support for using computer networks. 4. It should be designed to execute code from remote sources securely. 5. It should be easy to use by selecting what was considered the good parts of other object-oriented languages. Major release versions of Java, along with their release dates: JDK 1.0 (January 21, 1996) JDK 1.1 (February 19, 1997) J2SE 1.2 (December 8, 1998) J2SE 1.3 (May 8, 2000) J2SE 1.4 (February 6, 2002) J2SE 5.0 (September 30, 2004) Java SE 6 (December 11, 2006) Java SE 7 (July 28, 2011) Java SE 8 (March 18, 2014) 1

2 JAVA EE (Enterprise Edition) API - application programming interface Kogum vahendeid (API) erinevate lahenduste loomiseks: Veebi rakendused Veebi teenused Sõnumivahetus Andmebaasid Is a set of routines, protocols and tools for building software applications. Specifies ground rules Specifies how software components should interact with each ohter A good API makes it easier to develop a program by providing all the building blocks. A programmer then puts the blocks together JAVA EE Kogum vahendeid erinevate lahenduste loomiseks: Veebi rakendused Veebi teenused Sõnumivahetus Andmebaasis Web Container Servlet JSP Web Container Accepts requests, sends responses Manages component life cycles Routes requests to applications Web Containers Apache Tomcat JBoss WebLogic Jetty Glassfish Websphere Web Containers Multiple applications inside one container 2

3 Java source files Document root Static content 16 Configuration, executable code Deployment descriptor 3

4 Compiled classes Dependencies (JAR-s) Java Server Pages Deployment descriptor (web.xml) Instructs the container how to deal with this application <?xml version="1.0" encoding="utf-8"?> <web-app xmlns=" xmlns:xsi=" xsi:schemalocation=" version="3.0"> <welcome-file-list> <welcome-file>index.html</welcome-file> </welcome-file-list> </web-app> Deployment descriptor (web.xml) In Servlet API version 3.0 most components of web.xml are replaced by annotations that go directly to Java source code. We will see examples later Servlets On JAVA klass, mis töötleb sissetulevat päringut ning tagastab vastuse Enamasti kasutatakse HTTP päringu töötlemiseks ja tulemuse saatmiseks Servletid töötavad veebikonteineris, mis hoolitseb nende elutsükli ning päringute suunamise eest javax.servlet.http.httpservlet abstraktne klass, mis sisaldab meetodeid doxxx HTTP päringute töötlemiseks 4

5 Servlet example public class HelloServlet extends HttpServlet { Servleti protected void doget(httpservletrequest req, HttpServletResponse resp) throws ServletException, IOException { PrintWriter writer = resp.getwriter(); writer.println("<html><head><title>hello</title></head><body>"); writer.println("hello World!"); writer.println("current time: " + new Date() + ""); writer.println("</body></html>"); Mis on tulemuseks? HttpServlet methods For each HTTP method there is corresponding HttpServlet method dopost doget doput Servlet Mapping Before Servlet 3.0 in web.xml <servlet> <servlet-name>hello</servlet-name> <servlet-class>example.helloservlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>hello</servlet-name> <url-pattern>/hello</url-pattern> </servlet-mapping> Example Servlet Mapping Servlet life cycle In Servlet 3.0 via public class HelloServlet extends HttpServlet {

6 Üldine servleti elutsükkel Sessions Kui veebikonteineris puudub Servleti instants Laetakse Servleti klass Luuakse isend Initsialiseeritakse (init meetod) Iga päringu jaoks kutsutakse välja service meetod. Servleti kustutamisel kutsutakse välja destroy meetod Kus on päringumeetodid? HTTP is a stateless protocol, but we often need the server to remember us between requests. There are some ways: Cookies URL rewriting Java HttpSession Java HttpSession HttpSession is a common interface for accessing session context Actual implementation is provided by a Web Container HttpSession example HttpSession example HttpSession session = req.getsession(); int visit; if (session.isnew()) { visit = 0; else { visit = (Integer) session.getattribute("visit"); session.setattribute("visit", ++visit); Either create a new HttpSession session = req.getsession(); session or get existing int visit; if (session.isnew()) { visit = 0; else { visit = (Integer) session.getattribute("visit"); session.setattribute("visit", ++visit); 6

7 HttpSession example HttpSession example HttpSession session = req.getsession(); int visit; if (session.isnew()) { Check if the session is fresh or not visit = 0; else { visit = (Integer) session.getattribute("visit"); session.setattribute("visit", ++visit); HttpSession session = req.getsession(); int visit; if (session.isnew()) { visit = 0; else { Retrieve attribute visit = (Integer) session.getattribute("visit"); session.setattribute("visit", ++visit); HttpSession example HttpServletRequest - Attribute HttpSession session = req.getsession(); int visit; if (session.isnew()) { visit = 0; else { visit = (Integer) session.getattribute("visit"); session.setattribute("visit", ++visit); Update attribute Contains request information Also can be used to store attributes request.setattribute( key", value); request.getattribute( key ); HttpServletRequest: Parameter request.getparameternames(); Enumeration<String> String value = request.getparameter("name"); HttpServletRequest: Parameter vs Attribute Object value = request.getattribute( key ); String value = request.getparameter("name"); 7

8 HttpServletRequest: meta data HttpServletRequest: headers request.getmethod(); GET, POST, request.getremoteaddr(); Remote client s IP request.getservletpath(); /path/to/servlet request.getheadernames(); Enumeration<String> request.getheader("user-agent"); Mozilla/5.0 (X11; Linux x86_64) Request Headers Request Headers: Accept text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Encoding gzip, deflate Accept-Language et,et-ee;q=0.8,en-us;q=0.5,en;q=0.3 Connection keep-alive JSESSIONID=C687CC4E2B25B8A27DAB4A5F ; Cookie utma= ; oracle.uix=0^^gmt+3:00^p Host localhost:8080 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:19.0) User-Agent Gecko/ Firefox/19.0 Cookie HttpServletRequest: cookies Small piece of information (some ID, parameter, preference etc..) Stored in browser Usually sent by a server Client sends only name-value pair JSESSIONID = C687CC4E2B25B8A27DAB4A5F language=en Cookie parameters: Name Value Expires Path Domain Security (can be sent over ssh only) HttpOnly Cookie[] cookies = request.getcookies(); cookie.getname(); cookie.getvalue(); cookie.setvalue( new value ); 8

9 Cookie: HttpServletResponse Allows to set response information response.setheader("content-type", "text/html"); response.addcookie(new Cookie("name", "value")); Response Headers Response Headers: Content-Language Content-Type Date Server Transfer-Encoding et text/html;charset=utf-8 Mon, 11 Mar :48:54 GMT Apache-Coyote/1.1 chunked Request < > Response: HttpServletResponse: content response.getwriter().println("..."); Write text response.getoutputstream().write(...); Write binary 9

10 package org.apache.jsp.web_002dinf.jsp.document; import javax.servlet.*; import javax.servlet.http.*; import javax.servlet.jsp.*; import java.util.date; public final class testdokument_jsp extends org.apache.jasper.runtime.httpjspbase implements org.apache.jasper.runtime.jspsourcedependent { private static final javax.servlet.jsp.jspfactory _jspxfactory = javax.servlet.jsp.jspfactory.getdefaultfactory(); private static java.util.map<java.lang.string,java.lang.long> _jspx_dependants; private javax.el.expressionfactory _el_expressionfactory; private org.apache.tomcat.instancemanager _jsp_instancemanager; public java.util.map<java.lang.string,java.lang.long> getdependants() { return _jspx_dependants; public void _jspinit() { _el_expressionfactory = _jspxfactory.getjspapplicationcontext(getservletconfig().getservletcontext()).getexpressionfactory(); _jsp_instancemanager = org.apache.jasper.runtime.instancemanagerfactory.getinstancemanager(getservletconfig()); public void _jspdestroy() { public void _jspservice(final javax.servlet.http.httpservletrequest request, final javax.servlet.http.httpservletresponse response) throws java.io.ioexception, javax.servlet.servletexception { final javax.servlet.jsp.pagecontext pagecontext; javax.servlet.http.httpsession session = null; final javax.servlet.servletcontext application; final javax.servlet.servletconfig config; javax.servlet.jsp.jspwriter out = null; final java.lang.object page = this; javax.servlet.jsp.jspwriter _jspx_out = null; javax.servlet.jsp.pagecontext _jspx_page_context = null; try { response.setcontenttype("text/html; charset=utf-8"); pagecontext = _jspxfactory.getpagecontext(this, request, response, _jspx_page_context = pagecontext; application = pagecontext.getservletcontext(); config = pagecontext.getservletconfig(); session = pagecontext.getsession(); out = pagecontext.getout(); _jspx_out = out; out.write("\r\n"); out.write("\r\n"); out.write("current time: "); out.print( new Date() ); out.write(""); catch (java.lang.throwable t) { if (!(t instanceof javax.servlet.jsp.skippageexception)){ out = _jspx_out; if (out!= null && out.getbuffersize()!= 0) try { out.clearbuffer(); catch (java.io.ioexception e) { if (_jspx_page_context!= null) _jspx_page_context.handlepageexception(t); else throw new ServletException(t); finally { _jspxfactory.releasepagecontext(_jspx_page_context); null, true, 8192, true); Problem with servlets Java Server Pages (JSP) Writing HTML in Java is hideous PrintWriter writer = resp.getwriter(); writer.println("<html><head><title>hello</title></head><body>"); writer.println("hello World!"); writer.println("current time: " + new Date() + ""); writer.println("</body></html>"); Write HTML standard markup language Add dynamic scripting elements Add Java code JSP example JSP mapping war/web-inf/jsp/hello.jsp In web.xml <%@page import="java.util.date"%> <html> <head><title>hello</title></head> <body> hello World! current time: <%= new Date() %> </body> </html> <servlet> <servlet-name>hello2</servlet-name> <jsp-file>/web-inf/jsp/hello.jsp</jsp-file> </servlet> <servlet-mapping> <servlet-name>hello2</servlet-name> <url-pattern>/hello2</url-pattern> </servlet-mapping> JSP life cycle

11 Dynamic content Dynamic content Expression current time: <%= new Date() %> Scriptlet current time: <% out.println(new Date()); %> Declaration <%! private Date currentdate(){ return new Date(); %> current time: <%= currentdate() %> JSP Eeldefineeritud muutujad JSP Märgendid request- HttpServletRequest response HttpServletResponse out Writer session HttpSession application ServletContext pagecontext PageContext jsp:include Veebipäring antakse ajutiselt üle teisele JSP lehele. jsp:forward Veebpäring antakse jäädavalt üle teisele JSP lehele. jsp:getproperty Loeb JavaBeani muutuja väärtuse. jsp:setproperty Määrab JavaBeani muutuja väärtuse. jsp:usebean Loob uue või taaskasutab JSP lehele kättesaadavat JavaBeani. Expression Language (EL) Easy way to access JavaBeans in different scopes Rea summa: ${rida.summa * rida.kogus Basic Operators in EL Operator Description. Access a bean property or Map entry [] Access an array or List element ( ) Group a subexpression to change the evaluation order + Addition - Subtraction or negation of a value * Multiplication / or div Division % or mod Modulo (remainder) == or eq Test for equality!= or ne Test for inequality < or lt Test for less than > or gt Test for greater than <= or le Test for less than or equal >= or gt Test for greater than or equal && or and Test for logical AND or or Test for logical OR! or not Unary Boolean complement empty Test for empty variable values 11

12 Scopes Many objects allow you to store attributes ServletRequest.setAttribute HttpSession.setAttribute ServletContext.setAttribute Andmete skoobid ServletContext veebikontekst, üks ühe rakenduse ja JVM-i kohta Sessioon üks iga kasutajasessiooni kohta (erinev lehitseja = erinev sessioon) Request konkreetse päringu skoop Andmete kirjutamiseks/lugemiseks on meetodid setattribute/getattribute Scopes Scopes <% application.setattribute("subject", "Web information systems"); session.setattribute("topic", "Servlets"); request.setattribute("lector", "Roman"); pagecontext.setattribute("lector", "Roman"); %> Subject: ${subject Topic: ${topic Lector: ${lector Väljund: Subject: Web information systems Topic: Servlets Lector: Roman Scopes Scopes <% application.setattribute("subject", "Web information systems"); session.setattribute("topic", "Servlets"); request.setattribute("lector", "Roman"); pagecontext.setattribute("lector", "Roman"); pagecontext.setattribute("subject", "Meie uus teema"); application.setattribute("subject", "Meie järgmine teema"); %> Subject: ${subject Topic: ${topic Lector: ${lector Mis on väljundiks? <% application.setattribute("subject", "Web information systems"); session.setattribute("topic", "Servlets"); request.setattribute("lector", "Roman"); pagecontext.setattribute("lector", "Roman"); pagecontext.setattribute("subject", "Meie uus teema"); application.setattribute("subject", "Meie järgmine teema"); %> Subject: ${subject Topic: ${topic Lector: ${lector Subject: Meie uus teema Topic: Servlets Lector: Roman 12

13 Scopes JavaBeans <% application.setattribute("subject", "Web information systems"); session.setattribute("topic", "Servlets"); request.setattribute("lector", "Roman"); pagecontext.setattribute("lector", "Roman"); Less visible %> Subject: ${subject Topic: ${topic Lector: ${lector public class Person implements Serializable { private String name; public Person() { public String getname() { return name; public void setname(string name) { this.name = name; Public default constructor Implements Serializable getx and setx methods for each property X JavaBeans in EL Person person = new Person(); person.setname("roman"); request.setattribute("person", person); person: ${person.name Java Standard Tag Library (JSTL) Set of standard tools for JSP <% List<String> lectors = Arrays.asList("Siim", "Roman", "Margus"); pagecontext.setattribute("lectors", lectors); %> <c:set var="guestlector" value="margus" /> <c:foreach var="lector" items="${lectors"> Name: ${lector <c:if test="${lector eq guestlector >(guest)</c:if> </c:foreach> Problem with JSP Writing Java in JSP is hideous current time: <%= currentdate() %> Servlet + JSP JSP on puhtam Kihid on eraldatud Korduvkasutatavus Kuid kas saab paremini? Example 13

14 Model-View-Controller (MVC) Servlet controller, JSP view Controller gets invoked protected void doget(httpservletrequest req, HttpServletResponse resp) throws ServletException, IOException { req.setattribute("currentdate", new Date()); Model data req.getrequestdispatcher("/web-inf/jsp/hello.jsp").forward(req, resp); Servlet controller, JSP view Servlet controller, JSP view Controller gets invoked protected void doget(httpservletrequest req, HttpServletResponse resp) throws ServletException, IOException { req.setattribute("currentdate", new Date()); req.getrequestdispatcher("/web-inf/jsp/hello.jsp").forward(req, resp); Select and invoke view WEB-INF/jsp/hello.jsp <html>... <body> current time: ${currentdate </body> </html> View uses the data from model Filters Filter example Allows you to do something before, after or instead of servlet invocation. Filter chain public class LoggingFilter implements Filter { public void dofilter(servletrequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { long start = System.currentTimeMillis(); chain.dofilter(request, response); long end = System.currentTimeMillis(); System.out.println("Time spent: " + (end - start)); 14

15 Filter example Filter declaration public class LoggingFilter implements Filter { public void dofilter(servletrequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { long start = System.currentTimeMillis(); Invoke next filter in chain.dofilter(request, response); chain or the servlet if this was the last filter long end = System.currentTimeMillis(); System.out.println("Time spent: " + (end - start)); Before Servlet 3.0 in web.xml <filter> <filter-name>loggingfilter</filter-name> <filter-class>example.loggingfilter</filter-class> </filter> <filter-mapping> <filter-name>hello</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> Filter declaration Life cycle event listeners In Servlet 3.0 via public class LoggingFilter implements Filter {... javax.servlet.servletcontextlistener javax.servlet.servletcontextattributelistener javax.servlet.servletrequestlistener javax.servlet.servletrequestattributelistener javax.servlet.http.httpsessionlistener javax.servlet.http.httpsessionattributelistener Listener example Listener declaration public class LoggingRequestListener implements ServletRequestListener public void requestinitialized(servletrequestevent event) { System.out.println("Received request from " + public void requestdestroyed(servletrequestevent event) { Before Servlet 3.0 in web.xml <listener> <listener-class> example.loggingrequestlistener </listener-class> </listener> 15

16 Listener declaration Should I bother? In Servlet 3.0 via public class LoggingRequestListener implements ServletRequestListener {... There are a lot of fancy Java web frameworks that simplify application building. Should I still learn these basic technologies, will I ever use them? Should I bother? Should I bother? You are still going to deploy your application to a web container. Most traditional frameworks use JSP as the view technology. What about servlets? Sources of wisdom Most frameworks are based on the Servlet API You will probably still encounter things like HttpSession, HttpServletRequest etc inside your code. You might want to write filters and listeners. You probably won t write much servlets. But sometimes they can still be handy for simple tasks. AngularJS and REST (Representational State Transfer) Tutorial API 16