A brief introduction to the Java Knowledge Point of Tomcat

1 overview

This article mainly introduces the basic knowledge of Java

2 Basic Content

2.1 Introduction to programming languages

Hardware level: Microcode programming, assembly language

System level: c,c++, ...

Application level: java,php, Python, Ruby, Perl, C #, ...

Python:pvm

Standard Library

Web Framework:django,flask, ...

Java:jvm,jdk

Bash:bash Explainer

Program: Instruction + data

Program programming: Command-centric, data services in code;

Object-Oriented Programming: data-centric, Directive service to data;

Objects, methods (method)

2.2 Java History

The Java development process is as follows

1995:java1.0, Write once, Run Anywhere;

1996:JDK (Java Developmentkit), containing class libraries (APIs), development tools (Javac), JVM (SUN Classic VM)

JDK 1.0, APPLET,AWT

1997:JDK 1.1

1998:JDK 1.2

Sun splits Java technology into three directions:

J2se:standardedition

J2ee:enterpriseedition

J2me:mobileedition

Representative Technology: Ejb,java plugin, Swing,jit (Just in Time, instant compilation)

2000:JDK 1.3

HotSpot VMS

2002:JDK 1.4

2006:sun Open source Java technology, the GPL, the establishment of a known as OPENJDK organization;

Java 2 SE, Java 2 EE, Java 2 ME

2011:JDK 1.7

2014:JDK 1.8

2016:JDK 1.9

2.3 Running Java code

*.java (source code)--Javac-->*.class (bytecode)

Jvm:classloader, the class file of the loader, and the other class files to which the program's class file is dependent, then run; the entire run is represented as a JVM process;

. JSP-->jasper-->. Java--Javac-->.class---JVM

The code in JSP format is Jasper into. Java and then converted from Javac to. class format, loaded on the JVM virtual machine to run

Note: The output of the static output data to Java code based on Jasper, the result is the code of the servlet specification;

2.4 Java Technology System:

Java programming language

Java class file format

Java API

Java VMS: running Java code

Class Loader

Execution engine

JVM Run-time zone

Method Area: Thread sharing, used to store class information, constants, static variables, methods, etc. loaded by the JVM;

Heap: Is the largest part of the memory occupied by the JVM, and also the main area of GC management; storage object;

Java stack: Thread private, store thread's own local variables;

PC Register: Thread Private memory space, program instruction pointer;

Local method Stack:

2.5 Installing the JDK

Version has 1.6.0,1.7.0, 1.8.0 currently 8 is the mainstream version, so the experiment here are installed 8 version, multi-version coexistence, you can use the alternatives command to set the default version;

Note: After the installation is complete, to configure the Java_home environment variable, point to the Java installation path

OpenJDK:

Java_home=/usr

Oracle JDK:

Java_home=/usr/java/jdk_version

Java 2 EE:

Cgi:common Gateway Interface

Understanding the current Java environment, executing the command: java-version

2.5.1 Local Yum Installation

The Yum Warehouse is OPENJDK (open javadevelopment Kit) and is installed directly with Yum:

Yum Install Java-1.8.0-openjdk-devel

2.5.2 Oracle JDK:

Install the appropriate version of the RPM package; jdk-version-os-arch.rpm

Oracle Official download is the official JDK, the website found the package jdk-8u151-linux-x64.rpm, download link: http://download.oracle.com/otn-pub/java/jdk/8u151-b12/ e758a0de34e24606bca991d704f6dcbf/jdk-8u151-linux-x64.rpm

Introduction to JDK-8U151-LINUX-X64.RPM Package installation

RPM-IVH jdk-8u151-linux-x64.rpmvim/etc/profile.d/java.shexport java_home=/usr/java/latestexport PATH= $JAVA _home/ bin:/$PATH

Run after saving. /etc/profile.d/java.sh

The default version, latest is the latest version, which is specified as the latest version.

Java-version View Java version

Example: jdk-1.8.0_25-linux-x64.rpm

2.6 Servlet

To enable the Web server to collaborate with two different software systems for Web applications, a standard interface is required, and the servlet is one of the main interfaces.

class library; web App;

servlet container, servlet Engine

Jsp:java Server Page

Class Library:

JSP Container:
JSP + Servlet Container
Java Web Server:jws
Asf:jserv
2.7 Java Container
Business implementation
WebSphere, WebLogic, oc4j, Glassfish, Geronimo, Jonas,jboss, ...
WebSphere, takes up 40% of the share
WebLogic, takes up 30% of the share
JBoss, it's Red hat now.
Open Source Implementation
Tomcat, Jetty, Resin, ...
Tomcat: Written by the Java language, so you need to run the JVM, run up to Java programs, receive user requests, parse HTTP
Jetty, lightweight, very important when resources are scarce.
Resin Multi-Authorized distribution

 
  
 

This article is from the "Sunshine Ops" blog, please be sure to keep this source http://ghbsunny.blog.51cto.com/7759574/1982270
A brief introduction to the Java Knowledge Point of Tomcat