我在亚马逊的 AWS 工具包中遇到了一个基于 Java 的 DynamoDBMapper 的问题,该问题引发了“无法实例化类”异常错误。这是我第一次尝试使用 DBMapper,所以我不完全确定我的所有设置都正确。我的代码可以在下面找到:
public static void main(String[] args) {
dynamoDB = new AmazonDynamoDBClient(credentials);
DynamoDBMapper mapper = new DynamoDBMapper(dynamoDB);
PStatus data = mapper.load(PStatus.class, "online", new Integer(1655));
String assigned = data.getAssigned();
System.out.println(assigned);
}
@DynamoDBTable(tableName = "projectStatus")
public class PStatus {
private Integer projID;
private String status;
private String assigned;
@DynamoDBHashKey(attributeName = "status")
public String getStatus() { return status; }
public void setStatus(String status) { this.status = status; }
@DynamoDBRangeKey(attributeName = "projID")
public Integer getId() { return projID; }
public void setId(Integer projID) { this.projID = projID; }
@DynamoDBAttribute(attributeName = "assigned")
public String getAssigned() { return assigned; }
public void setAssigned(String assigned) { this.assigned = assigned; }
}
我基本上只是在尝试执行 GetItemRequest 然后绘制一个特定的属性,但是我得到了指向 line 的错误PStatus data = mapper.load(PStatus.class, "onFarm", new Integer(1655));
。我到底做错了什么?
编辑:下面的确切例外:
Exception in thread "main" com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMappingException: Failed to instantiate class
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.createKeyObject(DynamoDBMapper.java:325)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.load(DynamoDBMapper.java:313)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.load(DynamoDBMapper.java:212)
at test.TestGet.main(TestGet.java:20)
Caused by: java.lang.InstantiationException: test.TestGet$PStatus
at java.lang.Class.newInstance0(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper.createKeyObject(DynamoDBMapper.java:323)