实例
假设我们拥有一个运行良好的Eclipse IDE,并采取以下步骤来创建一个Spring应用程序:
- 创建一个名称为SpringExample的项目,并在创建的项目的src文件夹下创建一个包com.jc2182
- 使用“添加外部JAR”选项添加所需的Spring库,如“Spring Hello World示例”一章中所述。
- 在com.jc2182包下创建Java类Student 和 MainApp。
- 在src文件夹下创建Beans配置文件Beans.xml。
- 最后一步是创建所有Java文件和Bean配置文件的内容,然后按以下说明运行应用程序。
以下是Student.java内容。
package com.jc2182;
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();
}
}
以下是MainApp.java文件的内容。
package com.jc2182;
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");
HelloWorld objA = (HelloWorld) context.getBean("helloWorld");
objA.getMessage1();
objA.getMessage2();
HelloChina objB = (HelloChina) context.getBean("helloChina");
objB.getMessage1();
objB.getMessage2();
objB.getMessage3();
}
}
以下是配置文件的beans.xml它可以对基于setter方法注入配置
<?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:context = "http://www.springframework.org/schema/context"
xsi:schemaLocation = "http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:annotation-config/>
<!-- Definition for student bean -->
<bean id = "student" class = "com.jc2182.Student">
<property name = "name" value = "Zara" />
<!-- try without passing age and check the result -->
<!-- property name = "age" value = "11"-->
</bean>
</beans>
完成创建源和Bean配置文件后,尝试运行, 它将包含以下错误消息:
Error creating bean with name 'student' defined in class path resource [Beans.xml]: Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanInitializationException: Property 'age' is required for bean 'student'
接下来,您可以按照以下方式从“age”属性中删除注释,然后尝试上述示例-
<?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:context = "http://www.springframework.org/schema/context"
xsi:schemaLocation = "http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:annotation-config/>
<!-- Definition for student bean -->
<bean id = "student" class = "com.jc2182.Student">
<property name = "name" value = "Zara" />
<!-- try without passing age and check the result -->
<property name = "age" value = "11" />
</bean>
</beans>
上面的示例将产生以下结果: