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Today, I would like to share with you the relevant knowledge about how to apply the Java reflection mechanism. The content is detailed and the logic is clear. I believe most people still know too much about this, so share this article for your reference. I hope you can get something after reading this article. Let's take a look at it.

Trigger time of reflection

To understand when the reflection mechanism works, you must first understand the process of class loading. In the computer model defined by Von Neumann, any program needs to be loaded into memory to communicate with CPU. Bytecode .class files are no exception, and they need to be loaded into memory before they can be instantiated. Class loading is the process of instantiating a .class bytecode file into a java.lang.Class object and initializing it.

Common application scenarios of reflection

(1) typical application of reflection mechanism-Tomcat server

(2) Database-driven loading-use Class.forName () when using JDBC to connect to the database

(3) the bottom layer of framework design-- IOC control inversion of Spring framework.

(4) optimize the heavy and repetitive code

……

Reflection case demonstration

Business requirements: develop a tool class, on the basis of not modifying the code of the tool class, users only need to simply configure in the configuration file to complete the creation of objects and method calls.

Program design:

There are two heroes to choose from in the game.

Role 1: Angela

Occupation: Zhongdan

Skills: a way of using public to embellish a character's behavior in a program.

Passive: a method in which private is used in a program to represent the behavior of a character.

Character 2: Kay

Occupation: order

Skills: a way of using public to embellish a character's behavior in a program.

Passive: a method in which private is used in a program to represent the behavior of a character.

At this point, we need a configuration file for players to configure the hero characters they want to choose and the skills they want to release.

People.properties

Create a common maven project and use the reflection mechanism to implement the above business

Define role 1 AnQiLa:

Package com.demo.roles;public class AnQiLa {private String name= "Angela"; private String job= "Zhongdan"; / / method of privatizing roles to trigger Passive Skill private String getPassiveSkill () {return name+ ": [triggered Passive Skill!]" ;} / / role 1st Skill public String getFirstSkill () {return name+ ": [1st Skill is used in the middle];} public String getName () {return name;} public void setName (String name) {this.name = name;} public String getJob () {return job;} public void setJob (String job) {this.job = job }}

Define role 2:

Package com.demo.roles;public class Kai {private String name= "Kai"; private String job= "on order"; / / method of privatizing roles to trigger Passive Skill private String getPassiveSkill () {return name+ ": [triggered Passive Skill!]" ;} / / role 1st Skill public String getFirstSkill () {return name+ ": [1st Skill was used on the road];} public String getName () {return name;} public void setName (String name) {this.name = name;} public String getJob () {return job;} public void setJob (String job) {this.job = job }}

Define tool classes:

Package com.demo.controller;import java.io.InputStream;import java.lang.reflect.Method;import java.util.Properties;public class ReflectUtil {public static void main (String [] args) throws Exception {/ / load player configuration information Properties properties = new Properties (); ClassLoader classLoader = ReflectUtil.class.getClassLoader (); InputStream resourceAsStream = classLoader.getResourceAsStream ("people.properties"); properties.load (resourceAsStream) / / read the hero character selected by the player String role = properties.getProperty ("object.role") from the configuration file; / / read the skill String actions = properties.getProperty ("method.skills") used by the player from the configuration file; String [] skills = actions.split (",") / / instantiate the character object selected by the player through reflection Class aClass = Class.forName (role); Object instance = aClass.newInstance (); / / traverse the skill for that the player chooses to use (String skill: skills) {/ / get all the skills that the player uses the character Method declaredSkill = aClass.getDeclaredMethod (skill) / / determine whether the acquired skills are private if (declaredSkill.toString (). Contains ("private")) {/ / if it is a private Passive Skill, you need to set private skills to use declaredSkill.setAccessible (true); / / use passive Object invoke = declaredSkill.invoke (instance, null) System.out.println (invoke.toString ());} else {/ / if it is an ordinary skill, you can directly access Object invoke = declaredSkill.invoke (instance, null); System.out.println (invoke.toString ());}

The rest is as long as the player changes the configuration in the configuration file people.properties, and the tool class will help the player complete the character creation and skill release.

# players configure heroic roles to be selected

# Select AnQiLa [Angela]

Object.role=com.demo.roles.AnQiLa

# players configure the skills they need to use. Multiple skills are separated by English commas

# choose to use 1st Skill and trigger the private Passive Skill

Method.skills=getPassiveSkill,getFirstSkill

Run result 1:

Angela: [triggered Passive Skill!]

Angela: [1st Skill was used in the middle road]

Process finished with exit code 0

To change heroes, you can modify the contents of the configuration file:

# players configure heroic roles to be selected

# Select Kai [Kai]

Object.role=com.demo.roles.Kai

# players configure the skills they need to use. Multiple skills are separated by English commas

# choose to use 1st Skill and trigger the private Passive Skill

Method.skills=getPassiveSkill,getFirstSkill

Run result 2:

Kai: [triggered Passive Skill!]

Kay: [1st Skill was used on the road]

Process finished with exit code 0 and above are all the contents of the article "how to apply Java reflection Mechanism". Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.

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