正如你所知道的Java内部类是其他类的范围内定义的，同样，内部bean是被其他bean的范围内定义的bean。因此<property/>或<constructor-arg/>元素内<bean/>元件被称为内部bean和它如下所示。
<?
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-3.0.xsd"
>
<bean
id
=
"outerBean"
class
=
"..."
>
<property
name
=
"target"
>
<bean
id
=
"innerBean"
class
=
"..."
/>
</property>
</bean>
</beans>
例如：
我们使用Eclipse IDE，然后按照下面的步骤来创建一个Spring应用程序：
| 步骤 | 描述 |
|---|---|
| 1 | Create a project with a name SpringExample and create a package com.yiibai under the src folder in the created project. |
| 2 | Add required Spring libraries using Add External JARs option as explained in the Spring Hello World Example chapter. |
| 3 | Create Java classes TextEditor, SpellChecker and MainApp under the com.yiibaipackage. |
| 4 | Create Beans configuration file Beans.xml under the src folder. |
| 5 | The final step is to create the content of all the Java files and Bean Configuration file and run the application as explained below. |
这里是TextEditor.java文件的内容：
package
com
.
yiibai
;
public
class
TextEditor
{
private
SpellChecker
spellChecker
;
// a setter method to inject the dependency.
public
void
setSpellChecker
(
SpellChecker
spellChecker
)
{
System
.
out
.
println
(
"Inside setSpellChecker."
);
this
.
spellChecker
=
spellChecker
;
}
// a getter method to return spellChecker
public
SpellChecker
getSpellChecker
()
{
return
spellChecker
;
}
public
void
spellCheck
()
{
spellChecker
.
checkSpelling
();
}
}
下面是另外一个相关的类文件SpellChecker.java内容：
package
com
.
yiibai
;
public
class
SpellChecker
{
public
SpellChecker
(){
System
.
out
.
println
(
"Inside SpellChecker constructor."
);
}
public
void
checkSpelling
(){
System
.
out
.
println
(
"Inside checkSpelling."
);
}
}
以下是MainApp.java文件的内容：
package
com
.
yiibai
;
import
org
.
springframework
.
context
.
ApplicationContext
;
import
org
.
springframework
.
context
.
support
.
ClassPathXmlApplicationContext
;
public
class
MainApp
{
public
static
void
main
(
String
[]
args
)
{
ApplicationContext
context
=
new
ClassPathXmlApplicationContext
(
"Beans.xml"
);
TextEditor
te
=
(
TextEditor
)
context
.
getBean
(
"textEditor"
);
te
.
spellCheck
();
}
}
以下是配置文件beans.xml文件里面有配置为基于setter 注入，但使用内部bean：
<?
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-3.0.xsd"
>
<!-- Definition for textEditor bean using inner bean -->
<bean
id
=
"textEditor"
class
=
"com.yiibai.TextEditor"
>
<property
name
=
"spellChecker"
>
<bean
id
=
"spellChecker"
class
=
"com.yiibai.SpellChecker"
/>
</property>
</bean>
</beans>
创建源代码和bean配置文件来完成，让我们运行应用程序。如果一切顺利，这将打印以下信息：
Inside SpellChecker constructor.
Inside setSpellChecker.
Inside checkSpelling.
原文发布时间为：2018-10-21
本文作者：小白教程
