仅使用 hashKey 查询 dynamoDB

Posted 2023-04-14

【中文标题】仅使用 hashKey 查询 dynamoDB

【英文标题】：Query dynamoDB using only hashKey

【发布时间】：2016-12-25 02:39:54

【问题描述】：

我想只使用 Hashkey 来查询我的 dynamoDB。 我的 table(name = testTable) 架构如下：

字符串 autoID (HashKey) 字符串 AlexandriaID (RangeKey) 字符串文档类型

我的 dynamoDBQueryExpression 是：

---

String hashKey = "dummyHashKey";

testTable hashKeyValues = new testTable();

hashKeyValues.setAutoID(hashKey);

DynamoDBQueryExpression<testTable> queryExpression = new DynamoDBQueryExpression<testTable>();
queryExpression.withHashKeyValues(hashKeyValues);

//Assuming I have a dynamoDBMapper object mapper

List<testTable> docList = mapper.query(testTable.class, queryExpression);

---

我期待一个具有相同 autoID 的 testTable 对象列表。由于我是新手，如果我错了，请纠正我。

当我拨打mapper.query() 时没有任何反应。

引用 Vikdor 在 *** 问题上的评论 query using hashKey in dynamoDB

进一步修改：

我的确切查询方法：

public void queryFromRFIDocumentDetails(String hashKey)
    System.out.println((new Throwable()).getStackTrace()[0].toString() + "***Enter***");

    testTable hashKeyValues = new testTable();
    hashKeyValues.setAutoID(hashKey);

    System.out.println("AutoID for hashKeyValues " + hashKeyValues.getAutoID());
    System.out.println("DocTYpe for hashKeyValues " + hashKeyValues.getDocType());
    System.out.println("AlexandriaID for hashKeyValues " + hashKeyValues.getAlexandraiID());

    DynamoDBQueryExpression<testTable> queryExpression = new DynamoDBQueryExpression<testTable>();
    queryExpression.withHashKeyValues(hashKeyValues);
    queryExpression.withConsistentRead(false);

    System.out.println("calling mapper.query");  //nothing happens after this

    List<testTable> docList = new ArrayList<testTable>();
    docList = mapper.query(testTable.class, queryExpression);

    for(int i=0; i<docList.size(); i++)
        System.out.println("***iterating at retrieved index " + i);
        System.out.println("AutoID for retrieved document " + docList.get(i).getAutoID());
        System.out.println("DocTYpe for retrieved document " + docList.get(i).getDocType());
        System.out.println("AlexandriaID for retrieved document " + docList.get(i).getAlexandraiID());
    

我的程序的堆栈跟踪：

调用方法保存表中的对象：

***iterating at index 0
[java] AutoID for document to be saved abc
[java] DocTYpe for document to be saved foo
[java] AlexandriaID for document to be saved id1
[java] com.amazon.sduservice.db.dynamoDB.saveInRFIDocumentDetails(dynamoDB.java:201)***Enter***
[java] com.amazon.sduservice.db.dynamoDB.saveInRFIDocumentDetails(dynamoDB.java:203)***Exit***
[java] ***iterating at index 1
[java] AutoID for document to be saved abc
[java] DocTYpe for document to be saved foo
[java] AlexandriaID for document to be saved id2
[java] com.amazon.sduservice.db.dynamoDB.saveInRFIDocumentDetails(dynamoDB.java:201)***Enter***
[java] com.amazon.sduservice.db.dynamoDB.saveInRFIDocumentDetails(dynamoDB.java:203)***Exit***
[java] ***iterating at index 2
[java] AutoID for document to be saved abc
[java] DocTYpe for document to be saved foo
[java] AlexandriaID for document to be saved id3
[java] com.amazon.sduservice.db.dynamoDB.saveInRFIDocumentDetails(dynamoDB.java:201)***Enter***
[java] com.amazon.sduservice.db.dynamoDB.saveInRFIDocumentDetails(dynamoDB.java:203)***Exit***
[java] hashKey is abc

调用方法根据autoID查询表：

[java] com.amazon.sduservice.db.dynamoDB.queryFromRFIDocumentDetails(dynamoDB.java:207)***Enter***
[java] AutoID for hashKeyValues abc
[java] DocTYpe for hashKeyValues null
[java] AlexandriaID for hashKeyValues null
[java] calling mapper.query

对桌子的扫描操作输出：

Scanning Table RFIDocumentDetails
 [java] docType=S: foo,, autoID=S: abc,, alexandriaID=S: id1,
 [java] docType=S: foo,, autoID=S: abc,, alexandriaID=S: id2,
 [java] docType=S: foo,, autoID=S: abc,, alexandriaID=S: id3,
 [java] docType=S: pdf,, autoID=S: HashKey,, alexandriaID=S: alexandriaID1,
 [java] docType=S: pdf,, autoID=S: HashKey,, alexandriaID=S: alexandriaID2,
 [java] docType=S: foo,, autoID=S: asdf,, alexandriaID=S: id1,
 [java] docType=S: foo,, autoID=S: asdf,, alexandriaID=S: id2,
 [java] docType=S: foo,, autoID=S: foo,, alexandriaID=S: id1,
 [java] docType=S: foo,, autoID=S: foo,, alexandriaID=S: id2,
 [java] Scanning Table Finishes 

testTable 类：

public class testTable     
   private String autoID;   
   private String docType;  
   private String alexandriaID;     

   @DynamoDBHashKey(attributeName="autoID") 
   public String getAutoID()   return autoID; 
   public void setAutoID(String autoID)    this.autoID = autoID;      

   @DynamoDBRangeKey(attributeName="alexandriaID")  
   public String getAlexandraiID() return alexandriaID;   
   public void setAlexandriaID(String alexandriaID)    this.alexandriaID = alexandriaID;      

   @DynamoDBAttribute(attributeName="docType")  
   public String getDocType()  return docType;    
   public void setDocType(String docType)  this.docType = docType;    

【问题讨论】：

您的表是否包含 autoId 值“dummyHashKey”？

你迭代列表docList并检查结果了吗？

@notionquest 是的，在前面的步骤中，我使用 mapper.save() 在表中添加了多个对象，其中两个对象的 autoId 为“dummyHashKey”。在我的代码中，我已经在 mapper.query() 之后迭代列表，但是在调用 mapper.query() 之后没有任何反应。

你的意思是你在同一个程序中插入和读取同一个键？全部作为一个单元执行？如果是，请单独运行插入并单独阅读以调试问题。

@notionquest 是的，我正在以相同的方法进行这两个调用。让我把它们分开，然后再回复你。谢谢。

【参考方案1】：

如前所述，问题似乎出在 getAlexandraiID 声明中。

请按如下所述更改方法名称：-

发件人：-

public String getAlexandraiID() return alexandriaID; 

收件人：-

@DynamoDBRangeKey(attributeName = "alexandriaID")
public String getAlexandriaID() 
    return alexandriaID;