英文:
Unable to run the Spring Hello World program using Maven
问题
我正在学习Spring，并尝试在Spring中运行一个基本的Hello World程序。然而，在加载bean之后，我没有得到输出。
以下是我的代码：
beans.xml
<?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="HelloWorldBean" class="com.spring.test.HelloWorld">
<property name="message" value="Hello World!" />
</bean>
</beans>
HelloWorld.java
package com.spring.test;
public class HelloWorld {
private String message;
public String getMessage() {
return "Your message is - " + message;
}
public void setMessage(String message) {
this.message = message;
}
}
App.java（主类）
package com.spring.test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class App {
private static ApplicationContext context;
public static void main(String[] args) {
try {
context = new ClassPathXmlApplicationContext("classpath:beans.xml");
HelloWorld hw = (HelloWorld) context.getBean("HelloWorldBean");
hw.getMessage();
} catch (Exception e) {
e.printStackTrace();
}
}
}
我在我的Spring库中使用了4.3.12.RELEASE版本。
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.spring.test</groupId>
<artifactId>SpringHelloWorld</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>SpringHelloWorld</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<spring.version>4.3.12.RELEASE</spring.version>
</properties>
<dependencies>
<!-- 依赖项 -->
</dependencies>
</project>
以下是在Eclipse上的输出：
Aug 07, 2020 6:01:39 PM org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@25359ed8: startup date [Fri Aug 07 18:01:39 IST 2020]; root of context hierarchy
Aug 07, 2020 6:01:40 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [beans.xml]
提前感谢。任何帮助将不胜感激...
英文:
I am learning spring and trying to run a basic Hello World program in using spring.
However, post loading of beans, I don't get the output.
The following is my code -
beans.xml
<?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="HelloWorldBean" class="com.spring.test.HelloWorld">
<property name="message" value="Hello World!" />
</bean>
</beans>
HelloWorld.java
package com.spring.test;
public class HelloWorld {
private String message;
public String getMessage() {
return "Your message is - " + message;
}
public void setMessage(String message) {
this.message = message;
}
}
App.java (Main Class)
package com.spring.test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class App {
private static ApplicationContext context;
public static void main(String[] args) {
try {
context = new ClassPathXmlApplicationContext("classpath:beans.xml");
HelloWorld hw = (HelloWorld) context.getBean("HelloWorldBean");
hw.getMessage();
} catch (Exception e) {
e.printStackTrace();
}
}
}
Using 4.3.12.RELEASE for my spring libraries.
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.spring.test</groupId>
<artifactId>SpringHelloWorld</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>SpringHelloWorld</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<spring.version>4.3.12.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-expression</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
<version>1.1.1</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aspects</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-expression</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-instrument</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-instrument-tomcat</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jms</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-messaging</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-orm</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-oxm</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-test</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-tx</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc-portlet</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-websocket</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>
The below is output on eclipse
Aug 07, 2020 6:01:39 PM org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@25359ed8: startup date [Fri Aug 07 18:01:39 IST 2020]; root of context hierarchy
Aug 07, 2020 6:01:40 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [beans.xml]
Thanks in advance. Any help would be highly appreciated....
答案1
得分: 0
看起来您成功初始化了Bean，但没有对结果进行任何操作。确切地说，调用方法：
hw.getMessage();
本身不会执行任何操作，它只是检索一个值，然后被忽略。您可以改为输出这个值：
System.out.println(hw.getMessage());
英文:
Looks like you're successfully initializing the bean, but not doing anything with the result. To be precise, calling the method:
hw.getMessage();
Does not do anything by itself, it just retrieves a value that is then ignored. You could, instead, output this value:
System.out.println(hw.getMessage());
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