Spring-01-helloworld

The traditional HelloWorld

• Writing Java Classes

    package com.weixuan.spring;    publicclass HelloWorld {        publicvoidhello() {            System.out.println("Hello World .");                }        publicstaticvoidmain(String[] args) {        }    }

• compiling into a. class file
• Using ClassLoader to load class into the JVM
• New one instance
• All processes are fully involved

Using Spring's HelloWorld

• Write a Java class
• Write the configuration file, put the class into the spring container
• Start the spring container (look for the configuration file under the Classpath to instantiate the container)
• Remove the Java class from the container
• Object. Method
  Control Flip Concept: the creation of objects, initialization, destruction and other actions to the spring container to do, by the spring container to control the object's life cycle. Note: The destruction is in case of scope being a singleton

HelloWorld instances

HelloWorld class

package com.weixuan.spring;publicclass HelloWorld {    /**     * 属性是共享的，可能会引发线程安全问题     */    publicvoidhello() {        System.out.println("Hello World .");            }}

Configuration file

<?xml version= "1.0" encoding= "UTF-8"?><beans xmlns="Http://www.springframework.org/schema/beans"xmlns:xsi= "Http://www.w3.org/2001/XMLSchema-instance" xsi:schemalocation="Http://www.springframework.org/schema/beans Http://www.springframework.org/sch Ema/beans/spring-beans-2.5.xsd ">            <!--put a class in the spring container, the class becomes the first letter of the bean ID, lowercase ---    <bean id= "helloWorld" class=" Com.weixuan.spring.HelloWorld ">        <!--collaborators and configuration for this bean go    </Bean>    <!--more beans definitions Go</Beans>

Client test File
-Launch IOC container
-Remove class HelloWorld
-Use Object (object. method)

 PackageCom.weixuan.test;ImportOrg.junit.Test;ImportOrg.springframework.context.ApplicationContext;ImportOrg.springframework.context.support.ClassPathXmlApplicationContext;ImportCom.weixuan.spring.HelloWorld; Public  class testofhelloworld extends HelloWorld {    //Traditional notation    @Test     Public void Test() {HelloWorld HelloWorld =NewHelloWorld ();    Helloworld.hello (); }//using the IOC container notation    @Test     Public void TESTIOC() {/** * 1, launch IOC container 2, remove HelloWorld 3, object. Method */        //1. Launch IOC containerApplicationContext ApplicationContext =NewClasspathxmlapplicationcontext ("Com/weixuan/spring/applicationcontext.xml");//2, remove HelloWorldHelloWorld HelloWorld = (HelloWorld) applicationcontext. Getbean ("HelloWorld");//3, object. MethodHelloworld.hello (); }}

Scope property

@Test    publicvoidtestSpring() {        new ClassPathXmlApplicationContext(                "com/weixuan/spring/applicationContext.xml");        HelloWorld helloWorld1 = (HelloWorld) applicationContext                .getBean("helloWorld");        HelloWorld helloWorld2 = (HelloWorld) applicationContext                .getBean("helloWorld");        System.out.println(helloWorld1);        System.out.println(helloWorld2);    }

You can see that the output is the same, indicating that the default is a singleton mode

com.weixuan.spring.HelloWorld@42com.weixuan.spring.HelloWorld@42e366c1

The singleton mode takes into account thread safety issues, and you can set the scope property to be a prototype mode

<bean id="helloWorld" class="com.weixuan.spring2.HelloWorld" scope="prototype"></bean>

Additional Property configuration

• Init-method: After the constructor, there is a spring container that executes immediately, and the purpose of this method is to do some preparatory work before invoking the method after the constructor.
• Destroy-method: When the scope is set to Singleton, destroy this method when the spring container is closed or destroyed. Otherwise, the shutdown resource must be manually closed by the developer.
• Test file

 PackageCom.weixuan.initdestory; Public  class HelloWorld {     Public HelloWorld() {System.out.println ("Default constructor ..."); } Public void Init() {System.out.println ("Init ..."); } Public void Destory() {System.out.println ("Destory ..."); } Public void Hello() {System.out.println ("Hello world."); }}

<?xml version= "1.0" encoding= "UTF-8"?><beans xmlns="Http://www.springframework.org/schema/beans"xmlns:xsi= "Http://www.w3.org/2001/XMLSchema-instance" xsi:schemalocation="Http://www.springframework.org/schema/beans Http://www.springframework.org/sch Ema/beans/spring-beans-2.5.xsd ">            <!--put a class in the spring container, the class becomes the first letter of the bean ID, lowercase ---    <!--Init-method: After the constructor, there is a spring container that executes this method immediately after the constructor, before invoking the method, to do some preparatory work Destroy-method: When the scope is set When the spring container is closed or destroyed, the resource must be closed manually by the developer.    <bean id="HelloWorld" class="Com.weixuan.initdestory.HelloWorld"  Init-method="init" destroy-method="Destory" >                <!--collaborators and configuration for this bean go    </Bean>    <!--more beans definitions Go</Beans>

Test files and Results

 PackageCom.weixuan.test;ImportOrg.junit.Test;ImportOrg.springframework.context.ApplicationContext;ImportOrg.springframework.context.support.ClassPathXmlApplicationContext;ImportCom.weixuan.initdestory.HelloWorld; Public  class testofinitdestory extends HelloWorld {    PrivateApplicationContext ApplicationContext =NewClasspathxmlapplicationcontext ("Com/weixuan/initdestory/applicationcontext.xml");@Test     Public void Test() {HelloWorld HelloWorld = (HelloWorld) applicationcontext. Getbean ("HelloWorld"); Helloworld.hello ();/** * output, and no Destory method * Default constructor ... * Init ... * Hello world. */}@Test     Public void test2() {Classpathxmlapplicationcontext Classpathxmlapplicationcontext = (classpathxmlapplicationcontext) applicationCon        Text HelloWorld HelloWorld = (HelloWorld) classpathxmlapplicationcontext. Getbean ("HelloWorld");        Helloworld.hello (); Classpathxmlapplicationcontext.close ();/** * Scope defaults to singleton mode * This output: * default constructor ... * Init ... * Hello world. * .... * Destory ... * *        /** * Scope for prototype mode * output * Default constructor ... * Init ... * Hello world         . */}}

This is the simplest HelloWorld.

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

Spring-01-helloworld