added tutorial download a zip file from the internet

Author: Claudio Guidi

src/SUMMARY.md

@@ -26,6 +26,7 @@
     - [Advanced Scenarios](tutorials/advanced-scenarios/README.md)
         - [Implementing new port protocols in Jolie](tutorials/advanced-scenarios/supporting-new-protocols-in-jolie/README.md)
         - [Building a File Uploader Service](tutorials/advanced-scenarios/file-uploader/README.md)
+        - [Download a zip file from the Internet](tutorials/advanced-scenarios/download-zip-from-internet/README.md)
 
 # Language, tools, and standard library
 

src/tutorials/advanced-scenarios/download-zip-from-internet/README.md

@@ -0,0 +1,88 @@
+# Download a zip file from the Internet
+
+In this simple tutorial we'll see how to download derby.jar from _apache.org_.
+The full code can be downloaded [here](https://github.com/jolie/examples/blob/master/Tutorials/download-a-zip-from-the-web/download-a-zip-from-the-web.ol)
+
+The steps we'll follows are:
+
+
+1. Downloading the zip file `db-derby-10.14.2.0-lib.zip` with the libs from `https://archive.apache.org:443/dist/db/derby/db-derby-10.14.2.0/`
+1. Saving the downloaded file in the current directory
+1. Unzipping the file
+1. Extracting the file `derby.jar` and copying in teh current directory
+1. Removing unuseful directories
+
+## Downloading the zip file from the Internet
+In order to download the file we need to create an outputPort as it follows:
+
+```jolie
+...
+
+interface ApacheDerbyDownloadInterface {
+    RequestResponse:
+        downloadDerby
+}
+
+...
+
+outputPort ApacheDerby1_10_14 {
+    location: "socket://archive.apache.org:443/dist/db/derby/db-derby-10.14.2.0/"
+    protocol: https {
+        .osc.downloadDerby.alias = "db-derby-10.14.2.0-lib.zip"
+        .osc.downloadDerby.method = "get"
+    }
+    interfaces: ApacheDerbyDownloadInterface
+}
+
+...
+```
+
+Note that:
+
+1. The location is set without the name of the file, and the https token is replaced with medium `socket`
+1. The protocol https is defined in the parameter `protocol`
+1. The interface `ApacheDerbyDownloadInterface` has been attached to the outputPort where the operation `downloadDerby` is defined
+1. Protocol https is defines with two extra parameters `.osc.downloadDerby.alias` and `.osc.downloadDerby.method`. The former one defines an alias to use for making a request for operation _downloadDerby_, the latter one defines the http method to use when invoking the endpoint using operation _downloadDerby_
+
+In the behaviour, it is sufficient to program the related solicit-response:
+```jolie
+...
+downloadDerby@ApacheDerby1_10_14()( derby )
+...
+```
+Variable `derby` contains the downloaded file.
+
+## Saving the downloaded file
+This step is quite simple, just use the File standard library. Pay attentio to use the format `binary` for keeping safe the file encoding.
+```jolie
+writeFile@File( { filename = DOWNLOADED_ZIP, content << derby } )()
+```
+where `DOWNLOADED_ZIP` is a constant with the name of the file.
+
+## Unzipping the file
+Now it is possibile to unzip the file by using the standard library `zip-utils`
+
+```jolie 
+from zip-utils import ZipUtils
+...
+embed ZipUtils as ZipUtils
+...
+unzip@ZipUtils( { filename = DOWNLOADED_ZIP, targetPath = TARGET_PATH_UNZIP} )()
+```
+where `TARGET_PATH_UNZIP` is a constant with the target path where saving the unzipped files.
+
+## Extraction of the derby.jar file
+This step is quite simple because it is sufficient to exploit the standard library File
+
+```jolie
+derbyDbJarFilename = TARGET_PATH_UNZIP + "/db-derby-10.14.2.0-lib/lib/derby.jar"
+readFile@File( { filename = derbyDbJarFilename, format = "binary" } )( derbyJar )
+writeFile@File( { filename = "derby.jar", format = "binary", content << derbyJar })()
+```
+
+## Unuseful directories removal
+Also this step exploits the standard library for files
+```jolie
+delete@File( DOWNLOADED_ZIP )()
+deleteDir@File( TARGET_PATH_UNZIP )()
+```