Spring Feature--di

DI: Dependency Injection (Dependency injection), popular is a kind of XML configuration file, to the Sping container object initialization parameters. Also known as control reversal: inversion of the control (IoC)

There are two main forms of dependency injection:

|-: Dependency Injection based on construction method

|-: Dependency Injection based on setter method

the dependency injection based on the construction method can be divided into the following types:

• Complex data types:

• Simple data type:

|-based on attribute type

|-based on index (Index)

|-based on parameter names (name)

complex data type instances

Package com.fuwh.spring;

/* * Pojo Classes */public class Clazz {private String name;private int grade;Public String GetName () { return name;}public void SetName (String name) { THIS.name = name;}public int Getgrade () { return grade;}public void Setgrade (int grade) { This.grade = grade;}}package com.fuwh.spring;/* * Pojo Classes */public class Lesson {private String name;private int score;Public String GetName () { return name;}public void SetName (String name) { THIS.name = name;}public int Getscore () { return score;}public void SetScore (int score) { This.score = score;}}package Com.fuwh.spring;public class Student {Private Clazz Clazz;Private Lesson Lesson;Public Student (Clazz clazz, Lesson Lesson) { This.clazz = Clazz; This.lesson = lesson;}@OverridePublic String toString () { Return "Student [clazz=" + Clazz.getgrade () +clazz.getname () + ", lesson=" + lesson.getname () + "," +lesson.getscore () + "credits" ";}}

<?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.O Rg/schema/beans/spring-beans.xsd "> <!--configuration file--<bean id= "Student" class= "com.fuwh.spring.Student" lazy-init= "Default" > <constructor-arg ref= "Clazz"/> <constructor-arg ref= "Lesson"/></bean><bean id= "Clazz" class= "Com.fuwh.spring.Clazz" > <property name= "name" value= "Xin"/> <property name= "grade" Value= "/>"</bean><bean id= "Lesson" class= "Com.fuwh.spring.Lesson" > <property name= "name" value= "Java"/> <property name= "Score" value= "4"/></bean></beans>

Package com.fuwh.spring;

Import Org.springframework.context.applicationcontext;import Org.springframework.context.support.classpathxmlapplicationcontext;public class Spring01 {public static void Main (string[] args) { /* * Test class */ ApplicationContext ac=new classpathxmlapplicationcontext ("Bean.xml"); System.out.println (Ac.getbean ("Student", Student.class));}}

based on attribute type Example:

Package com.fuwh.spring;/* * Pojo Classes */public class Clazz {private String name;private int grade;Public Clazz (String name, int grade) { Super (); THIS.name = name; This.grade = grade;}@OverridePublic String toString () { Return "Student [name=" + name + ", grade=" + Grade + "]";}}<?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/schema/beans/spring-beans.xsd "> <!--Spring configuration file--<bean id= "Clazz" class= "Com.fuwh.spring.Clazz" lazy-init= "Default" > <constructor-arg type= "String" value= "Information and computational science"/> <constructor-arg type= "int" value= "/>"</bean></beans>

Package Com.fuwh.spring;import Org.springframework.context.applicationcontext;import Org.springframework.context.support.classpathxmlapplicationcontext;public class Spring01 {public static void Main (string[] args) { /* * Test class */// ApplicationContext ac=new classpathxmlapplicationcontext ("Bean.xml");// ApplicationContext ac=new Classpathxmlapplicationcontext (New string[]{"Beanstudent.xml", "BeanClazz.xml"});// ApplicationContext ac=new classpathxmlapplicationcontext ("Beanstudent.xml");// System.out.println (Ac.getbean ("student")); ApplicationContext ac=new classpathxmlapplicationcontext ("Beanclazz.xml"); System.out.println (Ac.getbean ("Clazz", Clazz.class));}}

An index-based (index) instance :

※ Note that the index starts with "0"
<?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.O Rg/schema/beans/spring-beans.xsd "> <!--Spring configuration file--<bean id= "Clazz" class= "Com.fuwh.spring.Clazz" lazy-init= "Default" > <constructor-arg index= "0" value= "Information and computational science"/> <constructor-arg index= "1" value= "/>"</bean></beans>

based on the argument name (name) instance :

<?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/schema/beans/spring-beans.xsd "> <!--Spring configuration file--<bean id= "Clazz" class= "Com.fuwh.spring.Clazz" lazy-init= "Default" > <constructor-arg name= "name" value= "Information and computational science"/> <constructor-arg name= "Grade" index= "1" value= "/>"</bean></beans>

Dependency Injection based on setter method

Package com.fuwh.spring;

/* * Pojo Classes */public class Lesson {private String name;private int score;public void SetName (String name) { SYSTEM.OUT.PRINTLN ("Name parameter is injected"); THIS.name = name;}public void SetScore (int score) { SYSTEM.OUT.PRINTLN ("Score parameter is injected"); This.score = score;}@OverridePublic String toString () { Return "Lesson [name=" + name + ", score=" + score + "credits]";}}

<?xml version= "1.0" encoding= "UTF-8"?>

<beans xmlns= "Http://www.springframework.org/schema/beans" xmlns:xsi= "http://www.w3.org/2001/ Xmlschema-instance "xmlns:p=" http://www.springframework.org/schema/p "xsi:schemalocation="/HTTP/ Www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd "> <!--S Pring configuration File--<bean id= "Lesson" class= "Com.fuwh.spring.Lesson" lazy-init= "Default" P:name= "PHP" P:score= "2"/></beans>

Package com.fuwh.spring;

Import Org.springframework.context.applicationcontext;import Org.springframework.context.support.classpathxmlapplicationcontext;public class Spring01 {public static void Main (string[] args) { /* * Test class */ ApplicationContext ac=new classpathxmlapplicationcontext ("Beanlesson.xml"); System.out.println (Ac.getbean ("Lesson", Lesson.class));}}

When injected, it is possible to use both of these methods, but in one of the following cases, only the setter can be used to inject

Class A constructs an instance of Class B, which requires an instance of Class A in the construction method of Class B.

At this time will be reported beancurrentlyincreationexception exception.

Spring Feature--di