This sections shows how to work with Cayenne in a web application.
The web part of the web application tutorial is done in JSP, which is the least common denominator of the Java web technologies, and is intentionally simplistic from the UI perspective, to concentrate on Cayenne integration aspect, rather than the interface. A typical Cayenne web application works like this:
For more information on the web application deployment, check Web Applications page.
So let's convert the tutorial that we created to a web application:
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd"> <web-app> <display-name>Cayenne Tutorial</display-name> <!-- This filter provides each request thread with a session-bound DataContext --> <filter> <filter-name>CayenneFilter</filter-name> <filter-class>org.apache.cayenne.conf.WebApplicationContextFilter</filter-class> </filter> <filter-mapping> <filter-name>CayenneFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
<%@ page language="java" contentType="text/html" %> <%@ page import="org.example.cayenne.persistent.*" %> <%@ page import="org.apache.cayenne.*" %> <%@ page import="org.apache.cayenne.query.*" %> <%@ page import="org.apache.cayenne.exp.*" %> <%@ page import="java.util.*" %> <% SelectQuery query = new SelectQuery(Artist.class); query.addOrdering(Artist.NAME_PROPERTY, SortOrder.ASCENDING); ObjectContext context = BaseContext.getThreadObjectContext(); List<Artist> artists = context.performQuery(query); %> <html> <head> <title>Main</title> </head> <body> <h2>Artists:</h2> <% if(artists.isEmpty()) {%> <p>No artists found</p> <% } else { for(Artist a : artists) { %> <p><a href="detail.jsp?id=<%=DataObjectUtils.intPKForObject(a)%>"> <%=a.getName()%> </a></p> <% } } %> <hr> <p><a href="detail.jsp">Create new artist...</a></p> </body> </html>
<%@ page language="java" contentType="text/html" %> <%@ page import="org.example.cayenne.persistent.*" %> <%@ page import="org.apache.cayenne.*" %> <%@ page import="java.util.*" %> <%@ page import="java.text.*" %> <% ObjectContext context = BaseContext.getThreadObjectContext(); String id = request.getParameter("id"); // find artist for id Artist artist = null; if(id != null && id.trim().length() > 0) { artist = DataObjectUtils.objectForPK(context, Artist.class, Integer.parseInt(id)); } if("POST".equals(request.getMethod())) { // if no id is saved in the hidden field, we are dealing with // create new artist request if(artist == null) { artist = context.newObject(Artist.class); } // note that in a real application we would so dome validation ... // here we just hope the input is correct artist.setName(request.getParameter("name")); artist.setDateOfBirthString(request.getParameter("dateOfBirth")); context.commitChanges(); response.sendRedirect("index.jsp"); } if(artist == null) { // create transient artist for the form response rendering artist = new Artist(); } String name = artist.getName() == null ? "" : artist.getName(); String dob = artist.getDateOfBirth() == null ? "" : new SimpleDateFormat("yyyyMMdd").format(artist.getDateOfBirth()); %> <html> <head> <title>Artist Details</title> </head> <body> <h2>Artists Details</h2> <form name="EditArtist" action="detail.jsp" method="POST"> <input type="hidden" name="id" value="<%= id != null ? id : "" %>" /> <table border="0"> <tr> <td>Name:</td> <td><input type="text" name="name" value="<%= name %>"/></td> </tr> <tr> <td>Date of Birth (yyyyMMdd):</td> <td><input type="text" name="dateOfBirth" value="<%= dob %>"/></td> </tr> <tr> <td></td> <td align="right"><input type="submit" value="Save" /></td> </tr> </table> </form> </body> </html>
To run the web application we'll use "maven-jetty-plugin". To activate it, let's add the following piece of code to the "pom.xml" file, following the "dependencies" section and save the POM:
<build> <plugins> <plugin> <groupId>org.mortbay.jetty</groupId> <artifactId>maven-jetty-plugin</artifactId> <version>6.1.22</version> </plugin> </plugins> </build>
[INFO] Scanning for projects... [INFO] ------------------------------------------------------------------------ [INFO] Building Unnamed - org.example.cayenne:tutorial:jar:0.0.1-SNAPSHOT [INFO] [INFO] Id: org.example.cayenne:tutorial:jar:0.0.1-SNAPSHOT [INFO] task-segment: [jetty:run] [INFO] ------------------------------------------------------------------------ ... [INFO] [jetty:run] [INFO] Configuring Jetty for project: Unnamed - org.example.cayenne:tutorial:jar:0.0.1-SNAPSHOT [INFO] Webapp source directory = /.../tutorial/Desktop/work/tutorial/src/main/webapp ... [INFO] Starting jetty 6.1.22 ... 2009-12-22 14:08:06.301::INFO: jetty-6.1.22 2009-12-22 14:08:06.474::INFO: No Transaction manager found - if your webapp requires one, please configure one. INFO: started configuration loading. INFO: loaded domain: UntitledDomain INFO: loaded <map name='UntitledDomainMap' location='UntitledDomainMap.map.xml'>. INFO: loading <node name='UntitledDomainNode' datasource='UntitledDomainNode.driver.xml' factory='org.apache.cayenne.conf.DriverDataSourceFactory' schema-update- strategy='org.apache.cayenne.access.dbsync.CreateIfNoSchemaStrategy'>. INFO: using factory: org.apache.cayenne.conf.DriverDataSourceFactory INFO: loading driver information from 'UntitledDomainNode.driver.xml'. INFO: loading driver org.apache.derby.jdbc.EmbeddedDriver INFO: loading user name and password. INFO: Created connection pool: jdbc:derby:memory:testdb;create=true Driver class: org.apache.derby.jdbc.EmbeddedDriver Min. connections in the pool: 1 Max. connections in the pool: 1 INFO: loaded datasource. INFO: no adapter set, using automatic adapter. INFO: loaded map-ref: UntitledDomainMap. INFO: finished configuration loading in 355 ms. 2009-12-22 14:08:07.081::INFO: Started SelectChannelConnector@0.0.0.0:8080 [INFO] Started Jetty Server
INFO: --- will run 1 query.
INFO: Opening connection: jdbc:derby:memory:testdb;create=true
Login: null
Password: *******
INFO: +++ Connecting: SUCCESS.
INFO: --- transaction started.
INFO: Detected and installed adapter: org.apache.cayenne.dba.derby.DerbyAdapter
INFO: No schema detected, will create mapped tables
INFO: CREATE TABLE GALLERY (ID INTEGER NOT NULL GENERATED BY DEFAULT AS IDENTITY,
NAME VARCHAR (200), PRIMARY KEY (ID))
INFO: CREATE TABLE ARTIST (DATE_OF_BIRTH DATE, ID INTEGER NOT NULL GENERATED
BY DEFAULT AS IDENTITY, NAME VARCHAR (200), PRIMARY KEY (ID))
INFO: CREATE TABLE PAINTING (ARTIST_ID INTEGER, GALLERY_ID INTEGER,
ID INTEGER NOT NULL GENERATED BY DEFAULT AS IDENTITY, NAME VARCHAR (200), PRIMARY KEY (ID))
INFO: ALTER TABLE PAINTING ADD FOREIGN KEY (ARTIST_ID) REFERENCES ARTIST (ID)
INFO: ALTER TABLE PAINTING ADD FOREIGN KEY (GALLERY_ID) REFERENCES GALLERY (ID)
INFO: CREATE TABLE AUTO_PK_SUPPORT ( TABLE_NAME CHAR(100) NOT NULL, NEXT_ID BIGINT NOT NULL, PRIMARY KEY(TABLE_NAME))
INFO: DELETE FROM AUTO_PK_SUPPORT WHERE TABLE_NAME IN ('ARTIST', 'GALLERY', 'PAINTING')
INFO: INSERT INTO AUTO_PK_SUPPORT (TABLE_NAME, NEXT_ID) VALUES ('ARTIST', 200)
INFO: INSERT INTO AUTO_PK_SUPPORT (TABLE_NAME, NEXT_ID) VALUES ('GALLERY', 200)
INFO: INSERT INTO AUTO_PK_SUPPORT (TABLE_NAME, NEXT_ID) VALUES ('PAINTING', 200)
INFO: SELECT t0.DATE_OF_BIRTH, t0.ID, t0.NAME FROM ARTIST t0 ORDER BY t0.NAME - prepared in 35 ms.
INFO: === returned 0 rows. - took 53 ms.
INFO: +++ transaction committed.
You are done with the tutorial!