the code
the first method
@Test
public void importProvince() throws IOException {
String fileName = "C:\\Users\\Windows3\\Documents\\province.json";
StringBuilder sb = new StringBuilder();
// 转换成List<String>, 要注意java.lang.OutOfMemoryError: Java heap space
List<String> lines = Files.readAllLines(Paths.get(fileName),
StandardCharsets.UTF_8);
lines.forEach(val -> sb.append(val));
System.out.println(sb.toString());
//objectMapperFace 是装饰器 里面是ObjectMapper
ObjectMapper objectMapper = objectMapperFace.getObjectMapper();
List<Pos> posList = objectMapper.readValue(sb.toString(), getCollectionType(List.class,Pos.class));
System.out.println(posList);
int dictValue = 1;
for (Pos pos : posList) {
List<City> citys = pos.getCity();
for (City city : citys) {
for (String area : city.getArea()) {
System.out.println(area);
}
}
}
}
/*
* 获取泛型的Collection Type
* @param collectionClass 泛型的Collection
* @param elementClasses 元素类
* @return JavaType Java类型
* @since 1.0
*/
public JavaType getCollectionType(Class<?> collectionClass, Class<?>... elementClasses) {
return objectMapperFace.getObjectMapper().getTypeFactory().constructParametricType(collectionClass, elementClasses);
}
The second method
TypeReference<List<Pos>> typeReference = new TypeReference<List<Pos>>() {
};
ObjectMapper objectMapper = objectMapperFace.getObjectMapper();
List<Pos> posList = objectMapper.readValue(sb.toString(), typeReference);
Effect
problems encountered
- Jackson from Array value (token
JsonToken.START_ARRAY
)
The JSON data and the field structure of the entity are inconsistent. I reported this error because the city field is an array, and the entity is written as an object.
- non-static inner classes like this can only by instantiated using default, no-argument constructor
Appears in the internal class, the class should add
static
keywords.