我有一个名为textfilewriter的bean将字符串实体写入hdfs。我已经在bean配置文件中配置了springbean。执行时，我得到nullpointerexception。请帮我解决这个问题。
我的bean配置：-

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/hadoop"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:beans="http://www.springframework.org/schema/beans"
    xmlns:hdp="http://www.springframework.org/schema/hadoop" 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/hadoop http://www.springframework.org/schema/hadoop/spring-hadoop.xsd">
    <hdp:configuration id="hadoopConfigBean">
        fs.defaultFS=${hdp.fs}
    </hdp:configuration>
    <beans:bean id="textFileWriter"
        class="org.springframework.data.hadoop.store.output.TextFileWriter">
        <beans:constructor-arg index="0" ref="hadoopConfigBean"></beans:constructor-arg>
        <beans:constructor-arg index="1"
            type="org.apache.hadoop.fs.Path" value="/user/mhduser"></beans:constructor-arg>
        <beans:constructor-arg index="2" type="org.springframework.data.hadoop.store.codec.CodecInfo" >
        <beans:null></beans:null>
        </beans:constructor-arg>
    </beans:bean>
    <context:property-placeholder location="hadoop-configs.properties" />
</beans:beans>

主要类别：-

public class MainApp {
    @Autowired
    TextFileWriter textFileWriter;
    public static void main(String[] args) {
        AbstractApplicationContext context = new ClassPathXmlApplicationContext(
                "/META-INF/spring/application-context.xml", MainApp.class); 
        System.out.println("Context loaded...");
        MainApp obj=new MainApp();
        obj.someMethod();
        context.registerShutdownHook();
    }
    private void someMethod() {
        try {
            textFileWriter.write("hi there");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

此行中出现空指针异常：-

textFileWriter.write("hi there");