java 如何正确和线程安全地重用 Jackson ObjectReader？
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How correctly and thread safe reuse Hymanson ObjectReader?
提问by Nawa
Hymanson have ObjectReader and documentation says that you need to use it for thread safety. But I can't understand how to do it correctly
Hymanson 有 ObjectReader 并且文档说你需要使用它来保证线程安全。但我不明白如何正确地做到这一点
import com.fasterxml.Hymanson.databind.ObjectMapper;
import com.fasterxml.Hymanson.databind.ObjectReader;
import java.io.IOException;
import java.util.Map;
public class JsonParser {
private ObjectMapper OBJECT_MAPPER = new ObjectMapper();
private ObjectReader OBJECT_READER = new ObjectMapper().readerFor(Map.class);
public Map<String, String> parseJson1(String json) throws IOException {
ObjectReader objectReader = OBJECT_MAPPER.readerFor(Map.class);
return objectReader.readValue(json);
}
public Map<String, String> parseJson2(String json) throws IOException {
return OBJECT_READER.readValue(json);
}
}
I wrote two samples
我写了两个样本
parseJson1()- creates ObjectReader from ObjectMapper on each parsingparseJson2()- reuses single instance on ObjectReader
parseJson1()- 在每次解析时从 ObjectMapper 创建 ObjectReaderparseJson2()- 在 ObjectReader 上重用单个实例
Which of them is right?
他们哪个是对的？
回答by vvg
Documentation said it's "fully thread-safe" it means you can use parseJson2safely without worring about invoking this method in concurrent threads.
文档说它是“完全线程安全的”，这意味着您可以parseJson2安全地使用，而不必担心在并发线程中调用此方法。
Uses "fluent" (or, kind of, builder) pattern so that instances are immutable (and thus fully thread-safe with no external synchronization); new instances are constructed for different configurations. Instances are initially constructed by ObjectMapper and can be reused, shared, cached; both because of thread-safety and because instances are relatively light-weight.
使用“流畅”（或某种构建器）模式，因此实例是不可变的（因此完全线程安全，没有外部同步）；新实例是为不同的配置构建的。实例最初由 ObjectMapper 构造，可以复用、共享、缓存；一方面是因为线程安全，另一方面是因为实例相对较轻。
