请问在这一段代码报错“空指针异常”的原因是什么？

Question

package com.manager;

import java.sql.Connection;
import java.sql.Statement;

import javax.sql.DataSource;

import org.springframework.jdbc.datasource.DataSourceUtils;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.support.TransactionCallback;
import org.springframework.transaction.support.TransactionTemplate;
import org.junit.Test;

public class TransactionExample {

DataSource datasource;
PlatformTransactionManager transactionManager;
TransactionTemplate transactionTemplate;
public DataSource getDatasource() {
    return datasource;
}
public void setDatasource(DataSource datasource) {
    this.datasource = datasource;
}
public PlatformTransactionManager getTransactionManager() {
    return transactionManager;
}
public void setTransactionManager(PlatformTransactionManager transactionManager) {
    this.transactionManager = transactionManager;
}
public TransactionTemplate getTransactionTemplate() {
    return transactionTemplate;
}
public void setTransactionTemplate(TransactionTemplate transactionTemplate) {
    this.transactionTemplate = transactionTemplate;
}

@Test
 public void transactionOperation(){
     transactionTemplate.execute(new TransactionCallback<Object>(){
         public Object doInTransaction(TransactionStatus status){
             Connection conn=DataSourceUtils.getConnection(datasource);
             try{
                 String sql="insert into user(name,password,age,sex,mobile)value('zhangsan','123456','37','male','123456')";
                 Statement stmt=conn.createStatement();
                 stmt.execute(sql);
                 stmt.execute(sql);
             }catch(Exception e){
                 transactionManager.rollback(status);
                 System.out.println("failed,rollback!");
                 System.out.println("reason:"+e.getMessage());
             }
             return null;
         }
     });
 }
}

问题出现在“transactionTemplate.execute(new TransactionCallback()”处，报错为“java.lang.NullPointerException
at com.manager.TransactionExample.transactionOperation(TransactionExample.java:41)
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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
”
望指正，谢谢！

Answer 1

transactionTemplate初始化的代码在哪？