I'm a beginner with spring and I am having problem with basic context init and I can't find any easy tutorial. So what I want to do is basic dependency injection and I have seen I only have to mark classes as @Componant or @Service and inject them directly within target fiels with @Autowired. For this I need to set properly my spring context (I'll need to build a web service + use JPA so I want to build a webapp)
I'm using JDK 1.8, maven 3.2.1
I want to do a basic dependency injection. => I want to inject a storeImpl instance there but this lead to a null pointer exception => this work perfectly without injection ( private Store storeImpl = new storeImpl(); )
package com.mycompany.app.controller;
@Controller
public class Controller
{
@Autowired
private Store storeImpl;
public void use()
{
storeImpl.get();
}
}
package com.mycompany.app.store;
public interface Store {
boolean get();
}
package com.mycompany.app.store;
@Component
public class StoreImpl implements Store {
@Override
public boolean get()
{
return true;
}
}
=> my main (I test my app with this for now):
public class App
{
public static void main(String[] args)
{
Controller controller = new Controller();
controller.use();
}
}
=> my 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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mycompany.app</groupId>
<artifactId>my-app</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<name>my-app</name>
<url>http://maven.apache.org</url>
<properties>
<spring.version>4.0.4.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.jsoup</groupId>
<artifactId>jsoup</artifactId>
<version>1.7.1</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.12.6</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</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-context-support</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>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework.data</groupId>
<artifactId>spring-data-jpa</artifactId>
<version>1.5.2.RELEASE</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>4.3.5.Final</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.0.1</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
=> my web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0">
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/META-INF/spring-context.xml</param-value>
</context-param>
<listener>
<listener-class>
org.springframework.web.context.ContextLoaderListener
</listener-class>
</listener>
</web-app>
=> my spring-context.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"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd">
<!--<context:component-scan base-package="com.mycompany.app"/>-->
<context:component-scan base-package="com.mycompany.app">
<!-- <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller" />-->
</context:component-scan>
</beans>
=> my project architecture
my-app
src
main
java
com.mycompagny.app
controller
Controller.java
store
Store.java
StoreImpl.java
app.java
ressources
META-INF
spring-context.xml
webapp
WEB-INF
web.xml
test
java
pom.xml
=> stacktrace of main()
Exception in thread "main" java.lang.NullPointerException
at com.mycompany.app.controller.Controller.run(Controller.java:25)
at com.mycompany.app.App.main(App.java:19)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
So my problem is my injected field (storeImpl) is null. And I think I miss something with context init ? Thanks again for your help and yourr grats answer