英文:
JPA Transactional method updates the column after already saving it
问题
我正在保存通过 REST Webservice POST 的一个对象，但在此之前我尝试更新一些字段。我有一个类 A，它有一个 B 作为其属性（没有关系，只是一个字段 - 复杂性由于该字段是一个单独的 JSON 字段/对象）。我试图在持久化 A 之前更新 B 的属性，这实际上运行得很好... 除了在插入新类之后，它还会更新该字段。类似这样的情况：
public class A {
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Id
Long id;
@Lob
@Convert(converter = BConverter.class)
B b_field;
}
public class B {
List<String> someVals;
List<Map<String, String>> amts;
}
@Converter
public class BConverter implements AttributeConverter<B, String> {
private final static ObjectMapper objectMapper = new ObjectMapper();
@Override
public String convertToDatabaseColumn(B b) {
try {
return objectMapper.writeValueAsString(b);
} catch (JsonProcessingException ex) {
// ...
return null;
}
}
@SneakyThrows
@Override
public B convertToEntityAttribute(String bVal) {
try {
return objectMapper.readValue(bVal, B.class);
} catch (IOException ex) {
// ...
return null;
}
}
}
这是持久化的 POST 方法：
@Override
@Transactional
public A saveA(A a) {
List<Map<String, String>> amts = new ArrayList<>();
amts.add(....这里放入一些哈希映射...);
a.getB_field.setAmts(amts);
return repository.save(a);
}
触发的查询是：
insert into A (id, b_field) -> 这里的 b_field 已经包含了上面添加的值
update A set b_field = ? where id = ? -> 同一个已经插入的对象。基本上是无用的
我可以想象这可能与事务提交有关，但不明白为什么它没有意识到没有任何更改。有什么想法吗？谢谢！
英文:
Im saving an Object that is POSTed in REST Webservice , but Im trying to update some fields just before that. I have an A class that has a B as its property (no relationship, just a field - complexity due to this field being a separate JSON field/object). I am trying to update B's property before A is persisted which actually works just fine.. EXCEPT after it inserts the new class , it also updates the field. Something like that:
public class A {
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Id
Long id;
@Lob
@Convert(converter = BConverter.class)
B b_field;
}
public class B {
List<String> someVals;
List<Map<String, String>> amts;
}
@Converter
public class BConverter implements AttributeConverter<B, String> {
private final static ObjectMapper objectMapper = new ObjectMapper();
@Override
public String convertToDatabaseColumn(B b) {
try {
return objectMapper.writeValueAsString(b);
} catch (JsonProcessingException ex) {....
return null;
}
}
@SneakyThrows
@Override
public B convertToEntityAttribute(String bVal) {
try {
return objectMapper.readValue(bVal, B.class);
} catch (IOException ex) {
......
return null;
}
}
}
Here is the POST method for persisting:
@Override
@Transactional
public A saveA(A a){
List<Map<String, String>> amts= new ArrayList<>();
amts.add(....here goes some hashmap...);
a.getB_field.setAmts(amts);
return repository.save(a);
}
Fired queries are:
insert into A (id, b_field) -> here b_field already contains the added values from above
update A set b_field =? where id=? -> same object that is already inserted. Basically useless
I can imagine it has to do with Transaction being committed, but dont understand why it doesnt get that there isnt any change. Any ideas? Thank you!!
答案1
得分: 0
似乎我自己离答案最近，至少目前是这样：
问题出在 Map 上打断了流程。涉及到 Maps 和 JPA 时有一些特殊情况，但直到现在在这种情况下仍然没有一个可行的方法。解决方法：如果我创建一个具有定义字段的类，而不是动态映射，它就能正常工作。<br>
更新：<br>
受到 @jccampanero 发布的链接的启发，我将 Map 更改为 JsonNode，并使用 JsonNodeFactory 动态构建节点。这个方法非常有效！
英文:
Seems like I came closest to an answer myself, at least for now:
it is the Map that breaks the flow. There are specialties when it comes to Maps and JPA, but still none of them worked for me till now in this case.
Workaround: If I create a class with defined fields instead of dynamic map it works great. <br>
UPDATE:<br>
Inspired by a link from @jccampanero, Ive changed Map to JsonNode and am building a node dynamically with JsonNodeFactory. That works like a charm!
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论