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");
2条答案
按热度按时间bvhaajcl1#
@Autowired
不会在这里工作,因为您正在使用类的新示例MainApp
这不是由spring管理的,这就是为什么你会得到一个NullPointerException
```MainApp obj=new MainApp();
obj.someMethod();
public class MainApp {
public MainApp(TextFileWriter textFileWriter){
this.textFileWriter = textFileWriter;
}
public MainApp(){
}
@Autowired
TextFileWriter textFileWriter;
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext(
"/META-INF/spring/application-context.xml");
System.out.println("Context loaded...");
}
private void someMethod() {
try {
textFileWriter.write("hi there");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
fhg3lkii2#
您仍然可以在不添加
MainApp
作为一个豆子。启用注解驱动配置。添加到
application-context.xml
下列的使Spring钢丝与