CODEWITHSUNDEEP
springdependency-injectioninversion-of-control
João Daniel
João Daniel

Reputation: 8986

Autowired field gives me null exception

I have a class that uses a method from a bean.

I'm trying to inject that method into my class using @Autowired, but it gives me NullPointerException.

public class ChangePasswordServiceImpl extends RemoteServiceServlet implements
        ChangePasswordService {

    @Autowired
    @Qualifier("userDetailsManager")
    private JdbcUserDetailsManager userDetailsManager;

    @Override
    public void changePassword(String oldPassword, String newPassword) {

        // This is the line that throws NullPointerException, i.e., userDetails
        // Manager is not being injected by Spring
        userDetailsManager.changePassword(oldPassword, newPassword);

    }

}

My xml file:

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:jdbc="http://www.springframework.org/schema/jdbc"
    xmlns:context="http://www.springframework.org/schema/context"

    xsi:schemaLocation="
             http://www.springframework.org/schema/beans
             http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
             http://www.springframework.org/schema/jdbc
             http://www.springframework.org/schema/jdbc/spring-jdbc-3.1.xsd
             http://www.springframework.org/schema/context
             http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <context:annotation-config/>

    <bean id="securityDataSource" class="org.apache.commons.dbcp.BasicDataSource"
        destroy-method="close">

        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="url"
            value="jdbc:mysql://localhost:3306/login" />
        <property name="username" value="root" />
        <property name="password" value="password" />
    </bean>

    <bean id="userDetailsManager"
        class="org.springframework.security.provisioning.JdbcUserDetailsManager">
        <property name="dataSource" ref="securityDataSource" />
        <property name="authenticationManager" ref="authenticationManager" />
        <qualifier value="userDetailsManager"/>
    </bean>

</beans>

Why is this field not being filled? Am I missing something?

Upvotes: 2

Views: 2114

Answers (1)

nicholas.hauschild
nicholas.hauschild

Reputation: 42849

Since ChangePasswordServiceImpl is not a Spring managed class (it is not in the xml configuration, therefore it is not a part of the ApplicationContext) @Autowired will do nothing for your class, which will cause you to get a NullPointerException when you try to use an instance of the class.

You should define a bean for ChangePasswordServiceImpl in your xml configuration, along with the rest that are currently there. 

<bean id="changePasswordService" class="the.package.ChangePasswordServiceImpl"/>

Finally, you can then get a hold of it via the ApplicationContext.

//assuming you are holding onto an instance of the ApplicationContext
ChangePasswordServiceImpl service = appContext.getBean("changePasswordService", ChangePasswordServiceImpl.class);
service.changePassword("old", "new");

Upvotes: 2

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