I have a HelloWorld Java project that uses Camel to obtain a Map, and print
out its contents in JSON format. The Map currently has hardcoded values,
but I really want to change my code so that it uses Spring to load a
sensor.properties file of nested key,value pairs into this Map.
I have another Java project I wrote that only uses Spring, and can load the
sensor.properties file just fine into an Arraylist object.
However, when I try to use code from that project to load the
sensor.properties in my HelloWorld project I get the following Camel error
with a NPE:
Returning Map
3310 [hello.world.request.timer] ERROR
org.apache.camel.processor.DefaultErrorHandler - Failed delivery for
exchangeId: 4e984884-df7f-4b82-a977-f5cf4c311814. Exhausted after
delivery attempt: 1 caught: java.lang.NullPointerException
java.lang.NullPointerException
at sample.SensorGenerator.getSensors(SensorGenerator.java:17)
at sample.HelloWorld.returnMap(HelloWorld.java:22)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at
org.apache.camel.component.bean.MethodInfo.invoke(MethodInfo.java:231)
at
org.apache.camel.component.bean.MethodInfo$1.proceed(MethodInfo.java:146)
at
org.apache.camel.component.bean.BeanProcessor.process(BeanProcessor.java:138)
org.apache.camel.management.InstrumentationProcessor.process(InstrumentationProcessor.java:67)
at
org.apache.camel.processor.DelegateProcessor.processNext(DelegateProcessor.java:53)
at
org.apache.camel.processor.DelegateProcessor.proceed(DelegateProcessor.java:82)
at
org.apache.camel.processor.interceptor.TraceInterceptor.process(TraceInterceptor.java:97)
at
org.apache.camel.management.InstrumentationProcessor.process(InstrumentationProcessor.java:67)
at
org.apache.camel.processor.RedeliveryErrorHandler.processExchange(RedeliveryErrorHandler.java:185)
at
org.apache.camel.processor.RedeliveryErrorHandler.processErrorHandler(RedeliveryErrorHandler.java:151)
at
org.apache.camel.processor.RedeliveryErrorHandler.process(RedeliveryErrorHandler.java:89)
at
org.apache.camel.processor.DefaultErrorHandler.process(DefaultErrorHandler.java:49)
at
org.apache.camel.processor.DefaultChannel.process(DefaultChannel.java:228)
at org.apache.camel.processor.Pipeline.process(Pipeline.java:75)
at
org.apache.camel.processor.UnitOfWorkProcessor.processNext(UnitOfWorkProcessor.java:70)
at
org.apache.camel.processor.DelegateProcessor.process(DelegateProcessor.java:48)
at org.
apache.camel.management.InstrumentationProcessor.process(InstrumentationProcessor.java:67)
at
org.apache.camel.component.timer.TimerConsumer.sendTimerExchange(TimerConsumer.java:102)
at
org.apache.camel.component.timer.TimerConsumer$1.run(TimerConsumer.java:49)
at java.util.TimerThread.mainLoop(Timer.java:555)
at java.util.TimerThread.run(Timer.java:505)
Is there something I need to add to my applicationContext.xml to tell Camel
that Spring will load my sensor.properties? Do I need to use the Spring
integration component specified at
http://camel.apache.org/springintegration.html ?
Here is my current ApplicationContext.xml:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans";
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
xmlns:camel="http://camel.apache.org/schema/spring";
xmlns:context="http://www.springframework.org/schema/context";
xmlns:util="http://www.springframework.org/schema/util";
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/util
http://www.springframework.org/schema/util/spring-util-3.0.xsd
http://camel.apache.org/schema/spring
http://camel.apache.org/schema/spring/camel-spring.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd";>
<bean
class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor"
/>
<context:component-scan base-package="sample" />
<context:annotation-config />
<camel:camelContext id="HelloWorldContext">
<camel:dataFormats>
<camel:json id="jack" library="Jackson"/>
</camel:dataFormats>
<camel:route>
<camel:from
uri="timer://hello.world.request.timer?fixedRate=true&period=10000"
/>
<camel:to
uri="log:hello.world.request?level=INFO?showAll=true" />
<camel:bean ref="helloWorld" />
<camel:marshal ref ="jack"/>
<camel:convertBodyTo type="java.lang.String" />
<camel:log message="${body}"/>
<camel:to
uri="log:hello.world.response?level=INFO?showAll=true" />
</camel:route>
</camel:camelContext>
<bean id="jms"
class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="configuration" ref="jmsConfig" />
</bean>
<bean id="jmsConfig"
class="org.apache.camel.component.jms.JmsConfiguration">
<property name="connectionFactory" ref="jmsConnectionFactory" />
<property name="transacted" value="false" />
<property name="concurrentConsumers" value="1" />
</bean>
<bean id="jmsConnectionFactory"
class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL" value="vm://localhost" />
<property name="redeliveryPolicy" ref="redeliveryPolicy" />
<property name="prefetchPolicy" ref="prefetchPolicy" />
</bean>
<bean id="prefetchPolicy"
class="org.apache.activemq.ActiveMQPrefetchPolicy">
<property name="queuePrefetch" value="5" />
</bean>
<bean id="redeliveryPolicy"
class="org.apache.activemq.RedeliveryPolicy">
<property name="maximumRedeliveries" value="1" />
<property name="backOffMultiplier" value="2" />
<property name="initialRedeliveryDelay" value="2000" />
<property name="useExponentialBackOff" value="true" />
</bean>
<util:properties id="sensorProperties"
location="classpath:/sensor.properties"/>
<bean class="sample.SensorGenerator">
<property name="sourceProperties" ref="sensorProperties" />
</bean>
</beans>
Here is are the four Java Classes I have (HelloWorldMain.java,
HelloWorld.java, Sensor.java, and SensorGenerator.Java):
HelloWorldMain.java:
package sample;
import org.springframework.context.support.AbstractApplicationContext;
import
org.springframework.context.support.ClassPathXmlApplicationContext;
public class HelloWorldMain {
// define context to load properties with Spring
public static void main(String[] args) throws Exception {
AbstractApplicationContext context = new
ClassPathXmlApplicationContext(
"applicationContext.xml");
Thread.currentThread().join();
}
}
HelloWorld.java:
package sample;
import java.util.*;
import org.apache.camel.Handler;
import org.springframework.stereotype.Service;
/**
* POJO that returns Hello World string
*
*/
@Service
public class HelloWorld {
@Handler
public Map<?, ?> returnMap(){
SensorGenerator sensorGenerator = new SensorGenerator();
System.out.println();
System.out.println("Returning Map");
// get the map of Sensors
Map<String,String> mySensorMap = sensorGenerator.getSensors();
// print out the Sensors in the map on the console
Set keys = mySensorMap.keySet();
for (Iterator i = keys.iterator(); i.hasNext();) {
String key = (String) i.next();
String value = (String) mySensorMap.get(key);
System.out.println("key= " + key + ", value= " + value);
}
return mySensorMap;
}
}
Sensor.java (which defines the fields I'm reading from sensor.properties):
package sample;
public class Sensor {
private String make;
private String makeDataType;
private String model;
private String modelDataType;
private String serialNumber;
private String serialNumberDataType;
private String sensorType;
private String sensorTypeDataType;
// getters and setters
public String getMake() {
return make;
}
public void setMake(String make) {
this.make = make;
}
public String getMakeDataType() {
return makeDataType;
}
public void setMakeDataType(String makeDataType) {
this.makeDataType = makeDataType;
}
public String getModel() {
return model;
}
public void setModel(String model) {
this.model = model;
}
public String getModelDataType() {
return modelDataType;
}
public void setModelDataType(String modelDataType) {
this.modelDataType = modelDataType;
}
public String getSerialNumber() {
return serialNumber;
}
public void setSerialNumber(String serialNumber) {
this.serialNumber = serialNumber;
}
public String getSerialNumberDataType() {
return serialNumberDataType;
}
public void setSerialNumberDataType(String serialNumberDataType) {
this.serialNumberDataType = serialNumberDataType;
}
public String getSensorType() {
return sensorType;
}
public void setSensorType(String sensorType) {
this.sensorType = sensorType;
}
public String getSensorTypeDataType() {
return sensorTypeDataType;
}
public void setSensorTypeDataType(String sensorTypeDataType) {
this.sensorTypeDataType = sensorTypeDataType;
}
}
SensorGenerator.java (the class where I current hard-code the properties but
want to have Spring load them from sensor.properties. If I comment out the
For loop and any lines referencing sourceProperties I can get the map
returned with the hard coded values just fine. That's why I suspect its
some sort of Spring/Camel integration issue):
package sample;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
public class SensorGenerator {
private Properties sourceProperties;
// variable to increment key number for each sensor
int sensorNumber = 1;
// method to inject sensor.properties into a Map using Spring
Map<String, String> getSensors() {
Map<String, String> sensorMap = new HashMap<String, String>();
for (Object key : sourceProperties.keySet()) {
// Separate out each of the key,value pairs as an entry
in the
// values array
String[] values = sourceProperties.getProperty((String)
key).split(
",");
System.out.println("values array size= " +
values.length);
// define string buffer that appends sensor number for
each sensor's
// keys. Ex: sensor1 would have s1make,
s1makeDataType, etc.
StringBuffer sensorNumberStringBuffer = new
StringBuffer();
sensorNumberStringBuffer.append("s");
sensorNumberStringBuffer.append(sensorNumber);
// make and its data type (with sensor number prefix)
StringBuffer makeStringBuffer = new StringBuffer();
makeStringBuffer.append(sensorNumberStringBuffer);
makeStringBuffer.append("make");
StringBuffer makeDataTypeStringBuffer = new
StringBuffer();
makeDataTypeStringBuffer.append(sensorNumberStringBuffer);
makeDataTypeStringBuffer.append("makeDataType");
// model and its data type (with sensor number prefix)
StringBuffer modelStringBuffer = new StringBuffer();
modelStringBuffer.append(sensorNumberStringBuffer);
modelStringBuffer.append("model");
StringBuffer modelDataTypeStringBuffer = new
StringBuffer();
modelDataTypeStringBuffer.append(sensorNumberStringBuffer);
modelDataTypeStringBuffer.append("modelDataType");
// serialNumber and its data type (with sensor number
prefix)
StringBuffer serialNumberStringBuffer = new
StringBuffer();
serialNumberStringBuffer.append(sensorNumberStringBuffer);
serialNumberStringBuffer.append("serialNumber");
StringBuffer serialNumberDataTypeStringBuffer = new
StringBuffer();
serialNumberDataTypeStringBuffer.append(sensorNumberStringBuffer);
serialNumberDataTypeStringBuffer.append("serialNumberDataType");
// sensorType and its data type (with sensor number
prefix)
StringBuffer sensorTypeStringBuffer = new
StringBuffer();
sensorTypeStringBuffer.append(sensorNumberStringBuffer);
sensorTypeStringBuffer.append("sensorType");
StringBuffer sensorTypeDataTypeStringBuffer = new
StringBuffer();
sensorTypeDataTypeStringBuffer.append(sensorNumberStringBuffer);
sensorTypeDataTypeStringBuffer.append("sensorTypeDataType");
/*
put all the key,value pairs for this sensor in the
sensorMap
*/
//TODO: Change all the hard coded values below to be
elements
// from the values array once Spring can load
spring.properties
// make and and its data type
sensorMap.put(makeStringBuffer.toString(), "DummyMake");
sensorMap.put(makeDataTypeStringBuffer.toString(),
"String");
// model and and its data type
sensorMap.put(modelStringBuffer.toString(),
"DummyModel");
sensorMap.put(modelDataTypeStringBuffer.toString(),
"String");
// serialNumber and and its data type
sensorMap.put(serialNumberStringBuffer.toString(),
"1234567890");
sensorMap.put(serialNumberDataTypeStringBuffer.toString(), "long");
// sensorType and its data type
sensorMap.put(sensorTypeStringBuffer.toString(),
"DummyType");
sensorMap.put(sensorTypeDataTypeStringBuffer.toString(), "String");
// increment for next sensor
sensorNumber++;
}
return sensorMap;
}
public void setSourceProperties(Properties properties) {
this.sourceProperties = properties;
}
}
Btw: Line 17 of SensorGenerator.java as mentioned in the stack trace above
is:
for (Object key : sourceProperties.keySet()) {
Here is an example sensor.properties file:
sensor1=DummySensor1:String,SensorModel1:String,1234567890:long,SensorType1:String
sensor2=DummySensor2:String,SensorModel2:String,8675309123:long,SensorType2:String
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