Jackson数据绑定文档指出Jackson支持反序列化“所有受支持类型的数组”，但我不知道它的确切语法。
对于单个对象，我会这样做:
//json input
{
"id" : "junk",
"stuff" : "things"
}
//Java
MyClass instance = objectMapper.readValue(json, MyClass.class);
现在对于一个数组，我想这样做:
//json input
[{
"id" : "junk",
"stuff" : "things"
},
{
"id" : "spam",
"stuff" : "eggs"
}]
//Java
List<MyClass> entries = ?
有人知道是否有一个魔法命令缺失了吗?如果不是，那么解决方案是什么?
当前回答
试试这个
List<MyClass> list = mapper.readerForListOf(MyClass.class).readValue(json)
其他回答
尤金·茨霍夫雷波夫报道
List<MyClass> myObjects = Arrays.asList(mapper.readValue(json, MyClass[].class))
这个解决方案对我来说似乎是最好的。
首先创建一个映射器:
import com.fasterxml.jackson.databind.ObjectMapper;// in play 2.3
ObjectMapper mapper = new ObjectMapper();
数组:
MyClass[] myObjects = mapper.readValue(json, MyClass[].class);
正如列表:
List<MyClass> myObjects = mapper.readValue(jsonInput, new TypeReference<List<MyClass>>(){});
另一种指定List类型的方法:
List<MyClass> myObjects = mapper.readValue(jsonInput, mapper.getTypeFactory().constructCollectionType(List.class, MyClass.class));
try {
ObjectMapper mapper = new ObjectMapper();
JsonFactory f = new JsonFactory();
List<User> lstUser = null;
JsonParser jp = f.createJsonParser(new File("C:\\maven\\user.json"));
TypeReference<List<User>> tRef = new TypeReference<List<User>>() {};
lstUser = mapper.readValue(jp, tRef);
for (User user : lstUser) {
System.out.println(user.toString());
}
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
对于通用实现:
public static <T> List<T> parseJsonArray(String json,
Class<T> classOnWhichArrayIsDefined)
throws IOException, ClassNotFoundException {
ObjectMapper mapper = new ObjectMapper();
Class<T[]> arrayClass = (Class<T[]>) Class.forName("[L" + classOnWhichArrayIsDefined.getName() + ";");
T[] objects = mapper.readValue(json, arrayClass);
return Arrays.asList(objects);
}
首先创建一个线程安全的ObjectReader实例。
ObjectMapper objectMapper = new ObjectMapper();
ObjectReader objectReader = objectMapper.reader().forType(new TypeReference<List<MyClass>>(){});
然后使用它:
List<MyClass> result = objectReader.readValue(inputStream);
