createNativeQuery [英] createNativeQuery

问题描述

在我的EJB项目中，我有一个带有以下方法的会话bean，该方法以日期和整数作为参数.

In my EJB project i have a session bean with the following method that takes in a date and integer as arguments.

public List<Receiptheader> retriveDetailedReceipts(String recDate, int poststatusid){
		System.out.println("******* "+ recDate + " ******** "+ poststatusid);		
		String query = "SELECT r.receiptnumber AS receiptnumber_, r.receiptdate AS receiptdate_, " +
				"r.receiptamount AS receiptamount_, r.postdate AS postdate_, " +
				"t.INTERFACETYPE AS interfacetype_, i.DESCRIPTION AS interfaces_ " +
				"FROM receiptheader r, interfacetypes t, interfaces i " +
				"WHERE r.INTERFACETYPEID = t.INTERFACETYPEID " +
				"AND r.INTERFACEID = i.INTERFACEID AND r.RECEIPTDATE = ''" + recDate +"'' "+
				"AND r.POSTSTATUSID = " + poststatusid;
		
		System.out.println(query);
		try{
			Query q = em.createNativeQuery(query,"Receiptdetail");	
			List<Receiptheader> rec = q.getResultList();
			return rec;
		}catch(Exception e){
			e.printStackTrace();
		}
    	return null;
    }
}

我在
的行上得到了java.lang.NullPointerException Query q = em.createNativeQuery(query,"Receiptdetail");

我在下面有一个实体

I am getting a java.lang.NullPointerException on the line with
Query q = em.createNativeQuery(query,"Receiptdetail");

I have an entity below

@Entity
@SqlResultSetMapping(name="Receiptdetail",
	      entities={ 
	            @EntityResult(entityClass=Receiptheader.class,
	            		fields={
    				@FieldResult(name="receiptnumber", column="receiptnumber_"),
    				@FieldResult(name="receiptdate", column="receiptdate_"), 
    				@FieldResult(name="receiptamount", column="receiptamount_"), 
    				@FieldResult(name="postdate", column="postdate_"), 
    				}),
				@EntityResult(entityClass=Interfacetypes.class,
	            		fields={
	            				@FieldResult(name="interfacetype", column="interfacetype_")
	            				}),
				@EntityResult(entityClass=Interfaces.class,
	            		fields={
	            				@FieldResult(name="description", column="interfaces_")
	            				})})
public class Receiptheader implements Serializable {

在我的代码中被称为我似乎无法理解错误是什么.请帮助

that is called in my code. I cant seem to understand what the error is. Please help

推荐答案

是否可能未初始化em?

em是局部变量.我认为问题是由于在构造函数中调用public List<Receiptheader> retriveDetailedReceipts(String recDate, int poststatusid)而引起的.我认为那是我的问题所在.如果我调用其他方法似乎在起作用.我认为在bean类的构造函数中调用方法可能会有问题.

em is a local variable. Im thinking the problem is arising because im calling public List<Receiptheader> retriveDetailedReceipts(String recDate, int poststatusid) in a constructor. I think thats where my problem is. If i call the method else where it seems to be working. I think there could be a problem with calling my method in the constructor of my bean class.

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