Cassandra -无法使用Java驱动程序解析元组列表
Cassandra -无法使用Java驱动程序解析元组列表
提问于 2016-11-18 01:29:11
我正在尝试使用Mapper访问存储在Cassandra中的元组数据结构。但是，我不能。我还没有在网上找到任何例子。
这是我创建的表和数据。
cqlsh:test> CREATE TABLE test.test_nested (id varchar PRIMARY KEY, address_mapping list<frozen<tuple<text,text>>>);
cqlsh:test> INSERT INTO test.test_nested (id, address_mapping) VALUES ('12345', [('Adress 1', 'pin1'), ('Adress 2', 'pin2')]);
cqlsh:test>
cqlsh:test> select * from test.test_nested;
id | address_mapping
-------+----------------------------------------------
12345 | [('Adress 1', 'pin1'), ('Adress 2', 'pin2')]
(1 rows)我的映射类(使用lombok作为builder、getter、setter)：
@Builder
@Table(keyspace = "test", name = "test_nested")
public class TestNested {
@PartitionKey
@Column(name = "id")
@Getter
@Setter
private String id;
@Column(name = "address_mapping")
@Frozen
@Getter
@Setter
private List<Object> address_mapping;
}我的映射器类:公共类TestNestedStore {
private final Mapper<TestNested> mapper;
public TestNestedStore(Mapper<TestNested> mapper) {
this.mapper = mapper;
}
public void insert(TestNested userDropData) {
mapper.save(userDropData);
}
public void remove(String id) {
mapper.delete(id);
}
public TestNested findByUserId(String id) {
return mapper.get(id);
}
public ListenableFuture<TestNested> findByUserIdAsync(String id) {
return mapper.getAsync(id);
}
}我正在尝试使用测试方法访问数据，如下所示：
@Test
public void testConnection2(){
MappingManager manager = new MappingManager(scyllaDBConnector.getSession());
Mapper<TestNested> mapper = manager.mapper(TestNested.class);
TestNestedStore testNestedStore = new TestNestedStore(mapper);
ListenableFuture<TestNested> fut = testNestedStore.findByUserIdAsync("12345");
Futures.addCallback(fut, new FutureCallback<TestNested>() {
@Override
public void onSuccess(TestNested testNested) {
}
@Override
public void onFailure(Throwable throwable) {
System.out.println("Call failed");
}
});
}位，我无法访问元组。我得到了这个错误：
java.lang.IllegalArgumentException: Error while checking frozen types on field address_mapping of entity com.example.model.TestNested: expected List to be not frozen but was frozen
at com.datastax.driver.mapping.AnnotationChecks.validateAnnotations(AnnotationChecks.java:73)
at com.datastax.driver.mapping.AnnotationParser.parseEntity(AnnotationParser.java:81)
at com.datastax.driver.mapping.MappingManager.getMapper(MappingManager.java:148)
at com.datastax.driver.mapping.MappingManager.mapper(MappingManager.java:105)我也尝试过使用private List<TupleValue> address_mapping;。但是没用！
如何通过cassandra的对象映射器访问元组值？
回答 1
Stack Overflow用户
发布于 2017-11-01 02:53:36
您可以将address_mapping定义为list<frozen<tuple<text,text>>>，即冻结的元组值的列表。要将此信息传递给MappingManager，您可以使用@FrozenValue attribute。
TestNested应该如下所示：
@Builder
@Table(keyspace = "test", name = "test_nested")
public class TestNested {
...
@Column(name = "address_mapping")
@Frozen
@Getter
@Setter
@FrozenValue
private List<Object> address_mapping;
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/40661390
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