SPRING3.0 official website of the Learning Notes document (VI)--3.4.1

3.4 Rely on
3.4.1 Dependency Injection
Dependency Injection two ways: Based on the constructor Di, setter-based method di.
3.4.1.1 based on the constructor di
parameter is the introduction of an object. and lack of parents before-subclass relationship:

 Package x.y;  Public class Foo {public   Foo (bar bar, Baz Baz) {      //...  }}

<Beans> <Bean ID="foo" class="X.y.foo"> <Constructor-arg ref="Bar"/> <Constructor-arg ref="Baz"/> </bean> <Bean ID="Bar" class="X.y.bar"/> <Bean ID="Baz" class="X.y.baz"/></beans>

When a simple type is used. Spring is not good at determining the type of value.

 PackageExamples Public classExamplebean {//No. of years to the calculate the Ultimate Answer  Private intyears;//The Answer to life, the Universe, and everything  PrivateString Ultimateanswer; PublicExamplebean (intYears, String Ultimateanswer) { This. Years = years; This. ultimateanswer = Ultimateanswer; }}

<Bean ID="Examplebean" class="examples. Examplebean "><Constructor-arg type="int" value="7500000"/><Constructor-arg type="Java.lang.String" value=" A"/></bean>

Or you can use index to specify the order in which the parameters are set.

<Bean ID="Examplebean" class="examples. Examplebean "><Constructor-arg Index="0" value="7500000"/><Constructor-arg Index="1" value=" A"/></bean>

For spirng3.0, you can also use name to specify the name of the property you want to set.

<Bean ID="Examplebean" class="examples. Examplebean "><Constructor-arg name="Years" value="7500000"/><Constructor-arg name="Ultimateanswer" value=" A"/></bean>

To get this method to work, remember:Your code must is compiled with the debug flag enabled (What do you mean? ) or to use @constructorproperties:

 PackageExamples Public classExamplebean {//Fields omitted@ConstructorProperties ({"Years","Ultimateanswer"}) PublicExamplebean (intYears, String Ultimateanswer) { This. Years = years; This. ultimateanswer = Ultimateanswer; }}

3.4.1.2 based on the setter method di

3.4.1.3 Dependency Parsing process
After the container is created. Each bean is validated with a valid validation of the property referenced by the Bean. However, the properties that the bean references are only created after the bean is created.

A singleton bean is created when the container is created. Other beans are only practical when they are requested.
Spring sets the properties or resolves dependencies as late as possible.

A depends on B, then B is created first and then A is created.
3.4.1.4 di Example
Use the static factory method to pass the number of references.

<Bean ID="Examplebean" class="examples. Examplebean "    Factory-method="CreateInstance"><Constructor-arg ref="Anotherexamplebean"/><Constructor-arg ref="Yetanotherbean"/><Constructor-arg value="1"/></bean><Bean ID="Anotherexamplebean" class="examples. Anotherbean "/><Bean ID="Yetanotherbean" class="examples. Yetanotherbean "/>

 Public classExamplebean {//A private constructor  PrivateExamplebean (...) {    ...  }//a static factory method; The arguments to this method can be  //Considered the dependencies of the bean is returned,  //Regardless of how those arguments is actually used.   Public StaticExamplebean CreateInstance (Anotherbean anotherbean, Yetanotherbean Yetanotherbean,inti) {Examplebean EB =NewExamplebean (...);//Some other operations ...      returnEb }}

    

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SPRING3.0 official website of the Learning Notes document (VI)--3.4.1