Weather monitor - Revision history

Christian: /* Querying the Database */ removed minor detail

2013-04-07T11:16:55Z

‎Querying the Database: removed minor detail

Christian: /* Querying the Database */ added detail where to set copyXML

2013-04-01T13:15:33Z

‎Querying the Database: added detail where to set copyXML

Christian: /* Receiver */ link to picture

2013-03-27T20:47:42Z

‎Receiver: link to picture

Christian: /* Filling Database */ link to source file

2013-03-27T20:24:39Z

‎Filling Database: link to source file

Christian: /* Filling Database */ added predefined make rules

2013-03-27T20:13:11Z

‎Filling Database: added predefined make rules

Christian: /* Filling Database */ C program and Makefile

2013-03-27T19:59:13Z

‎Filling Database: C program and Makefile

Christian: /* Protocol between Receiver and Server */ ASCII string format

2013-03-27T19:46:11Z

‎Protocol between Receiver and Server: ASCII string format

Christian: /* Protocol between Receiver and Server */ USB-to-serial chip

2013-03-27T19:31:32Z

‎Protocol between Receiver and Server: USB-to-serial chip

Christian: /* REST Server */ added details about Jersey

2013-03-17T15:06:13Z

‎REST Server: added details about Jersey

Christian: /* Querying the Database */

2013-03-17T14:54:46Z

‎Querying the Database

@@ Line 90: / Line 90: @@
 This library uses rrdtool's ''pipe mode'': It calls <code>"rrdtool -"</code> which causes rrdtool to wait for commands from stdin and output its responses to stdout. This mode is also very fast, because the rrdtool instance only needs to be started once and from then on serves all requests.
-The tricky part is to configure the place of the database file differently depending on which machine it runs on (development machine or server). I decided to use Tomcat's ''Context Parameters''. I configured the context in <code>META-INF/context.xml</code> which resides in the deployable WAR file and is copied to a machine-specific directory upon first deployment (<code>Server/Service/Engine/Host@copyXML</code> must be <code>true</code> in <code>/etc/tomcat7/server.xml</code>). There I can modify it to fit the corresponding machine configuration. To access this context parameter in the source code I have to do the following:
+The tricky part is to configure the place of the database file differently depending on which machine it runs on (development machine or server). I decided to use Tomcat's ''Context Parameters''. I configured the context in <code>META-INF/context.xml</code> which resides in the deployable WAR file and is copied to a machine-specific directory upon first deployment. There I can modify it to fit the corresponding machine configuration. To access this context parameter in the source code I have to do the following:
 <pre>@javax.ws.rs.core.Context
 public void setServletContext(ServletContext context) throws IOException {

@@ Line 90: / Line 90: @@
 This library uses rrdtool's ''pipe mode'': It calls <code>"rrdtool -"</code> which causes rrdtool to wait for commands from stdin and output its responses to stdout. This mode is also very fast, because the rrdtool instance only needs to be started once and from then on serves all requests.
-The tricky part is to configure the place of the database file differently depending on which machine it runs on (development machine or server). I decided to use Tomcat's ''Context Parameters''. I configured the context in <code>META-INF/context.xml</code> which resides in the deployable WAR file and is copied to a machine-specific directory upon first deployment. There I can modify it to fit the corresponding machine configuration. To access this context parameter in the source code I have to do the following:
+The tricky part is to configure the place of the database file differently depending on which machine it runs on (development machine or server). I decided to use Tomcat's ''Context Parameters''. I configured the context in <code>META-INF/context.xml</code> which resides in the deployable WAR file and is copied to a machine-specific directory upon first deployment (<code>Server/Service/Engine/Host@copyXML</code> must be <code>true</code> in <code>/etc/tomcat7/server.xml</code>). There I can modify it to fit the corresponding machine configuration. To access this context parameter in the source code I have to do the following:
 <pre>@javax.ws.rs.core.Context
 public void setServletContext(ServletContext context) throws IOException {

@@ Line 15: / Line 15: @@
 == Receiver ==
 For receiving the 868,35 MHz signals the following device from ELV is used:
 * [http://www.elv.de/usb-wetterdaten-empfaenger-usb-wde1-komplettbausatz.html USB-Wetterdaten-Empfänger USB-WDE1]

@@ Line 64: / Line 64: @@
 * Call the <code>rrd_update_r()</code> function to enter these values into the RRDB.
-The complete C code can be found here ('''TODO''').
+The complete C code can be found here: '''[[File:weathermon.c]]'''.
 To compile it I use the following short <code>Makefile</code> (note that it makes heavy use of predefined rules). Using an extra <code>Makefile</code> was only necessary for including the <code>librrd.so</code> library.

@@ Line 68: / Line 68: @@
 To compile it I use the following short <code>Makefile</code> (note that it makes heavy use of predefined rules). Using an extra <code>Makefile</code> was only necessary for including the <code>librrd.so</code> library.
-<pre>LDLIBS = /usr/lib/librrd.so
+<pre># predefined rule that compiles .c files into .o files: $(CC) $(LDFLAGS) n.o $(LOADLIBES) $(LDLIBS)
 weathermon : weathermon.c</pre>

@@ Line 57: / Line 57: @@
 == Filling Database ==
 Serial data coming from the receiver must be interpreted and then stored into the database.
 == Querying the Database ==

@@ Line 36: / Line 36: @@
 usbserial              34545  1 cp210x
 </pre>
-From then on the USB-WDE1 will transmit a serial ASCII string whenever a new measurement has been received.
+From then on the USB-WDE1 will transmit a serial ASCII string whenever a new measurement has been received. This can be verified with the following commands:
 == Protocol between Server and Clients ==

@@ Line 30: / Line 30: @@
 = Interfaces =
 == Protocol between Receiver and Server ==
 == Protocol between Server and Clients ==
 * REST with JSON

← Older revision		Revision as of 15:06, 17 March 2013
Line 59:		Line 59:
	== REST Server ==		== REST Server ==
	The web server implements a [http://en.wikipedia.org/wiki/Representational_state_transfer REST] service which clients use to query data from the database. It is implemented in Java and uses the [http://jersey.java.net/ Jersey] framework.		The web server implements a [http://en.wikipedia.org/wiki/Representational_state_transfer REST] service which clients use to query data from the database. It is implemented in Java and uses the [http://jersey.java.net/ Jersey] framework.
		+
		+	A very good introduction to implementing REST services with Jersey can be found here:
		+	* http://www.vogella.com/articles/REST/article.html
		+
		+	Basically, you only need to do the following:
		+	* setup the deployment descriptor (<code>WEB-INF/web.xml</code>)
		+	* implement the service class with using the correct annotations
		+
		+	The '''web.xml''' needs to contain the following information:
		+	<pre><?xml version="1.0" encoding="UTF-8"?>
		+	<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
		+	<display-name>weatherserv</display-name>
		+	<servlet>
		+	<servlet-name>Jersey REST Service</servlet-name>
		+	<servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
		+	<init-param>
		+	<param-name>com.sun.jersey.config.property.packages</param-name>
		+	<param-value>at.ettisoft.weatherserv</param-value>
		+	</init-param>
		+	</servlet>
		+	<servlet-mapping>
		+	<servlet-name>Jersey REST Service</servlet-name>
		+	<url-pattern>/rest/*</url-pattern>
		+	</servlet-mapping>
		+	</web-app></pre>
		+
		+	* The servlet container is implemented by Jersey, therefore the node <code>web-app/servlet/servlet-class</code> must point to ''com.sun.jersey.spi.container.servlet.ServletContainer''.
		+	* This container expects the parameter <code>com.sun.jersey.config.property.packages</code> to point to the service classes at ''at.ettisoft.weatherserv''

@@ Line 52: / Line 52: @@
 The tricky part is to configure the place of the database file differently depending on which machine it runs on (development machine or server). I decided to use Tomcat's ''Context Parameters''. I configured the context in <code>META-INF/context.xml</code> which resides in the deployable WAR file and is copied to a machine-specific directory upon first deployment. There I can modify it to fit the corresponding machine configuration. To access this context parameter in the source code I have to do the following:
-<code>@Context
+<pre>@javax.ws.rs.core.Context
-	public void setServletContext(ServletContext context) throws IOException {
+public void setServletContext(ServletContext context) throws IOException {
-		servletContext = context;
+  servletContext = context;
-		String rrdbdir = servletContext.getInitParameter("rrdbdir");</code>
+  String rrdbdir = servletContext.getInitParameter("rrdbdir");</pre>
 == REST Server ==
 The web server implements a [http://en.wikipedia.org/wiki/Representational_state_transfer REST] service which clients use to query data from the database. It is implemented in Java and uses the [http://jersey.java.net/ Jersey] framework.