Using Groovy to start a server on the command line
by Luciano Fiandesio, Andrey Adamovich
Groovy 2 Cookbook
- Groovy 2 Cookbook
- Table of Contents
- Groovy 2 Cookbook
- Credits
- About the Authors
- About the Reviewers
- www.PacktPub.com
- Preface
- 1. Getting Started with Groovy
- Introduction
- Installing Groovy on Windows
- Installing Groovy on Linux and OS X
- Executing Groovy code from the command line
- Using Groovy as a command-line text file editor
- Using Groovy to start a server on the command line
- Running Groovy with invokedynamic support
- Building Groovy from source
- Managing multiple Groovy installations on Linux
- Using groovysh to try out Groovy commands
- Starting groovyConsole to execute Groovy snippets
- Configuring Groovy in Eclipse
- Configuring Groovy in IntelliJ IDEA
- 2. Using Groovy Ecosystem
- Introduction
- Using Java classes from Groovy
- Embedding Groovy into Java
- Compiling Groovy code
- Simplifying dependency management with Grape
- Integrating Groovy into the build process using Ant
- Integrating Groovy into the build process using Maven
- Integrating Groovy into the build process using Gradle
- Generating documentation for Groovy code
- Checking Groovy code's quality with CodeNarc
- 3. Using Groovy Language Features
- Introduction
- Searching strings with regular expressions
- Writing less verbose Java Beans with Groovy Beans
- Inheriting constructors in Groovy classes
- Adding the cloning functionality to Groovy Beans
- Defining code as data in Groovy
- Defining data structures as code in Groovy
- Implementing multiple inheritance in Groovy
- Adding a functionality to the existing Java/Groovy classes
- Defining type-checking rules for dynamic code
- Adding automatic logging to Groovy classes
- 4. Working with Files in Groovy
- Introduction
- Reading from a file
- Reading a text file line by line
- Processing every word in a text file
- Writing to a file
- Replacing tabs with spaces in a text file
- Filtering a text file's content
- Deleting a file or directory
- Walking through a directory recursively
- Searching for files
- Changing file attributes on Windows
- Reading data from a ZIP file
- Reading an Excel file
- Extracting data from a PDF
- 5. Working with XML in Groovy
- 6. Working with JSON in Groovy
- 7. Working with Databases in Groovy
- Introduction
- Creating a database table
- Connecting to an SQL database
- Querying an SQL database
- Modifying data in an SQL database
- Calling a stored procedure
- Reading BLOB/CLOB from a database
- Building a simple ORM framework
- Using Groovy to access Redis
- Using Groovy to access MongoDB
- Using Groovy to access Apache Cassandra
- 8. Working with Web Services in Groovy
- Introduction
- Downloading content from the Internet
- Executing an HTTP GET request
- Executing an HTTP POST request
- Constructing and modifying complex URLs
- Issuing a REST request and parsing a response
- Issuing a SOAP request and parsing a response
- Consuming RSS and Atom feeds
- Using basic authentication for web service security
- Using OAuth for web service security
- 9. Metaprogramming and DSLs in Groovy
- Introduction
- Querying methods and properties
- Dynamically extending classes with new methods
- Overriding methods dynamically
- Adding performance logging to methods
- Adding a caching functionality around methods
- Adding transparent imports to a script
- DSL for executing commands over SSH
- DSL for generating reports from logfiles
- 10. Concurrent Programming in Groovy
- Introduction
- Processing collections concurrently
- Downloading files concurrently
- Splitting a large task into smaller parallel jobs
- Running tasks in parallel and asynchronously
- Using actors to build message-based concurrency
- Using STM to atomically update fields
- Using dataflow variables for lazy evaluation
- Index
In this recipe, we continue to explore the groovy command's features at one's disposal. This time, we show how to create a process capable of serving client requests through TCP/IP directly from the command line and with one line of code.
The command-line option that we are going to use for this purpose is -l:
- By using the
-loption, it is trivial to start a simple socket server in Groovy:groovy -l 4444 -e "println new Date()" - The previous line will start a server that listens to port 4444 and returns the date and time string for every line of data it receives from the clients:
groovy is listening on port 4444 - In order to test whether the server actually works, you can start any telnet-like program (for example, KiTTY, if you are on Windows) to connect to a localhost on port 4444, and type any string (for example,
What time is it?), and press Enter. The server should reply with a date/time string back as shown in the following screenshot:
In this way, you can quite easily organize communication channels for ad hoc notifications on different hosts.
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