嘿,我的 Json 也有问题
[
{
"aimid": "12345"
},
{
"aimid": "333674"
},
{
"aimid": [
"4568999",
"6789345"
]
}]
这是我的 Pojo 类:-
@JsonProperty("aimid")
private String aimid;
public String getAimid() {
return aimid;
}
public void setAimid(String aimid) {
this.aimid = aimid;
}
我想将amiid存储在pojo中。当我在我的应用程序中像上面那样编写时,我收到错误。
com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.lang.String` out of START_ARRAY token.
根据我的理解,我因为数组元素而收到错误,所以任何人都可以建议我如何捕获这两个东西,如果它作为字符串出现或它作为数组字符串出现
最佳答案
挑战在于,在某些情况下“aimid”是一个字符串值,但在另一种情况下它是一个数组。
如果您可以控制 JSON 的结构,则更新该结构,以便根数组的每个元素都具有以下结构之一:
字符串 { “目标”:“333674” } 或数组 { “目标”:[ “4568999”, “6789345” ] }
如果您无法控制数据的结构,则需要自己解析数据并将其处理到 POJO 中。
请参阅这 3 个代码示例,它们应该说明如何采用这种方法。 :
public class MyPojo {
private List<String> aimid;
@JsonProperty("aimid")
public List<String> getAimid() {
return aimid;
}
@JsonProperty("aimid_array")
public void setAimid(final List<String> aimid) {
this.aimid = aimid;
}
@JsonProperty("aimid")
public void setAimid(final String aimid) {
this.aimid = Arrays.asList(aimid);
}
}
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.node.*;
import java.io.IOException;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.junit.Test;
public class UnitTest {
private static final Logger LOGGER = Logger.getLogger(UnitTest.class.getName());
public UnitTest() {
}
@Test
public void testOneAimId() throws IOException {
final String json = "[\n"
+ "{\n"
+ " \"aimid\": \"12345\"\n"
+ "},\n"
+ "{\n"
+ " \"aimid\": \"333674\"\n"
+ "}]";
final List<MyPojo> result = new ObjectMapper().readValue(json, new TypeReference<List<MyPojo>>() {
});
log(Level.SEVERE, LOGGER, "testOneAimId", result);
}
@Test
public void testListAimIds() throws IOException {
final String json = "[\n"
+ "{\n"
+ " \"aimid_array\": [\n" // HERE WE HAVE CHANGED THE JSON PROP NAME
+ " \"4568999\",\n"
+ " \"6789345\"\n"
+ " ]\n"
+ "}]";
final List<MyPojo> result = new ObjectMapper().readValue(json, new TypeReference<List<MyPojo>>() {
});
log(Level.SEVERE, LOGGER, "testListAimIds", result);
}
@Test
public void testMixed() throws IOException {
final String json = "[\n"
+ "{\n"
+ " \"aimid\": \"12345\"\n"
+ "},\n"
+ "{\n"
+ " \"aimid\": \"333674\"\n"
+ "},\n"
+ "{\n"
+ " \"aimid_array\": [\n" // HERE WE HAVE CHANGED THE JSON PROP NAME
+ " \"4568999\",\n"
+ " \"6789345\"\n"
+ " ]\n"
+ "}]";
final List<MyPojo> result = new ObjectMapper().readValue(json, new TypeReference<List<MyPojo>>() {
});
log(Level.SEVERE, LOGGER, "testMixed", result);
}
@Test
public void testMixed2() throws IOException {
final String json = "[\n"
+ "{\n"
+ " \"aimid\": \"12345\"\n"
+ "},\n"
+ "{\n"
+ " \"aimid\": \"333674\"\n"
+ "},\n"
+ "{\n"
+ " \"aimid\": [\n"
+ " \"4568999\",\n"
+ " \"6789345\"\n"
+ " ]\n"
+ "}]";
final JsonNode result = new ObjectMapper().readValue(json, JsonNode.class);
final ArrayList<String> arrayList = new ArrayList<>();
result.forEach((final JsonNode jsonNode) -> {
if (jsonNode.getNodeType() != JsonNodeType.OBJECT)
throw new IllegalArgumentException(jsonNode.toString());
final ObjectNode obj = (ObjectNode) jsonNode;
obj.forEach(o -> {
switch (o.getNodeType()) {
case ARRAY:
final ArrayNode array = (ArrayNode) o;
array.forEach(t -> arrayList.add(t.asText()));
break;
case STRING:
arrayList.add(o.asText());
break;
default:
throw new IllegalArgumentException(o.toString());
}
});
});
final MyPojo myPojo = new MyPojo();
myPojo.setAimid(arrayList);
log(Level.SEVERE, LOGGER, "myPojo", myPojo);
}
private void log(final Level level, final Logger logger, final String title, final Object obj) {
try {
if (title != null)
logger.log(level, title);
final ObjectWriter writer = new ObjectMapper().writerWithDefaultPrettyPrinter();
logger.log(level, obj == null ? "null" : writer.writeValueAsString(obj));
} catch (final JsonProcessingException ex) {
logger.log(Level.SEVERE, ex.getMessage(), ex);
}
}
}
关于java - jackson 错误: Cannot deserialize instance of `java.lang.String` out of START_ARRAY token,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/60524352/