NOTE: The behaviors in this article are for HotSpot, other JVM might behave differently.
What is JVM?
The Java Virtual Machine is the cornerstone of the Java platform. It is the component of the technology responsible for its hardware- and operating system independence, the small size of its compiled code, and its ability to protect users from malicious programs.
The Java Virtual Machine is an abstract computing machine. Like a real computing machine, it has an instruction set and manipulates various memory areas at run time. The JVM doesn’t understand Java typo, that’s why you compile your *.java files to obtain *.class files that contain the bytecodes understandable by the JVM.
Today, the Spring Framework was released to 4.2 RC2. In Spring 4.2, better application events and Server-Sent Event(SSE) are supported.
In this article, I’ll introduce you to the two new features.
What’s Server-Sent Event
Server-sent events (SSE) is a technology where a browser receives automatic updates from a server via an HTTP connection. The Server-Sent Events EventSource API is standardized as part of HTML5 by the W3C.
Server-sent event is a standard describing how servers can initiate data transmission toward clients once an initial client connection has been established. They are commonly used to send message updates or continuous data streams to a browser client and are designed to enhance native, cross-browser streaming through a JavaScript API called EventSource, through which a client requests a particular URL in order to receive an event stream.
This guide walks you through the process of creating a “hello world” application that sends messages back and forth, between a browser and the server. WebSocket is a very thin, lightweight layer above TCP. It makes it very suitable to use “subprotocols” to embed messages. In this guide, we’ll dive in and use STOMP messaging with Spring to create an interactive web application.
Maven Dependencies
First, we need to add the Spring messaging modules in the POM file:
Last few months, I’m working on a project with Spring MVC and Hibernate. Now, I want to try MyBatis. In this article, I’ll tell you how to useMyBatis with Spring MVC.
According to Wikipedia, database transactions should provide an “all-or-nothing” proposition, stating that each work-unit performed in a database must either be completed in its entirety or have no effect whatsoever. Further, the system must isolate each transaction from other transactions, results must conform to existing constraints in the database, and transactions that complete successfully must get written to durable storage.
Introduction
Verwandlung Online Judge is a cross-platform online judge system based on the Spring MVC Framework.
The application used the following components:
- Spring MVC Framework
- Druid Database Connection Pool
- CodeMirror Editor
- ActiveMQ
The architecture of the project can be described as follows:
Code Repository
Screenshots
A few days ago, I created TestZilla on Aliyun Elastic Compute Service.
However, with the increment of PV, I decided to use CDN to cache static files(images, CSS, and javascript).
But there’s no information on how to use CDN with Spring MVC, so I asked a question on StackOverflow.
Setup Spring Configuration
First of all, you need to use PropertyPlaceholderConfigurer in Spring Configuration(such as dispatcher-servlet.xml)
<!-- Property File Location -->
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>classpath:/testzilla.properties</value>
</list>
</property>
</bean>
<util:properties id="propertyConfigurer" location="classpath:/testzilla.properties"/>
<context:property-placeholder properties-ref="propertyConfigurer" />
Of course, you need to add XML Namespaces:
This tutorial provides a sample spring MVC application that allows user sending an e-mail message.
In this tutorial, you are supposed to familiar with Java EE development as well as developing Spring MVC-based applications.
Spring Framework’s Support for E-mail
Based on JavaMail, Spring framework provides high-level abstraction API which greatly simplifies e-mail sending process. Let’s take a brief look at this API in the following class diagram:
To send e-mail messages, we can use an implementation of interface MailSender – the JavaMailSenderImpl class which is built upon on JavaMail. It’s convenient to configure this implementation as a bean in Spring’s context:
Almost all collections in Java are derived from the java.util.Collection interface. Collection defines the basic parts of all collections. The interface states the add() and remove() methods for adding to and removing from a collection respectively. Also required is the toArray() method, which converts the collection into a simple array of all the elements in the collection. Finally, the contains() method checks if a specified element is in the collection. The Collection interface is a subinterface of java.lang.Iterable, so any Collection may be the target of a for-each statement. (The Iterable interface provides the iterator() method used by for-each statements.) All collections have an iterator that goes through all of the elements in the collection. Additionally, Collection is a generic. Any collection can be written to store any class. For example, Collection can hold strings, and the elements from the collection can be used as strings without any casting required.