我從 API 接收這個 JSON。
{
"message" : "message",
"1": {
"packageCode": "packageCode1",
"packageNum": "packageNum1"
},
"2": {
"packageCode": "packageCode2",
"packageNum": "packageNum2"
}
}
是否可以將其轉換為具有以下屬性的 java 物件？
- 字串訊息
- 包 [] 包
我正在使用 jackson-databind ObjectMapper。
謝謝！
uj5u.com熱心網友回復：
最好更改 API，它回傳此 JSON 以回傳一組包。
{
"message" : "message",
"packages": [
{
"packageCode": "packageCode1",
"packageNum": "packageNum1"
},
{
"packageCode": "packageCode2",
"packageNum": "packageNum2"
}]
}
如果無法更改，則需要通過擴展StdDeserializer<T>該類來撰寫自定義去實作器。您必須以編程方式檢查JsonNode決議樹并組裝所需的物件。
該文章介紹了如何做到這一點，并配備了一個作業代碼示例。
uj5u.com熱心網友回復：
我找到了這個作業解決方案，使用自定義解串器！我定義了允許的最大包數，但如果不需要，可以洗掉此檢查。
班級回應：
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import lombok.Getter;
import lombok.Setter;
import lombok.ToString;
@Getter
@Setter
@ToString
@JsonDeserialize(using = ResponseDeserializer.class)
public class Response {
private String message;
private Package [] packages;
}
課程包：
import lombok.Getter;
import lombok.Setter;
import lombok.ToString;
@Getter
@Setter
@ToString
public class Package {
private String packageCode;
private String packageNum;
}
類ResponseDeserializer：
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.deser.std.StdDeserializer;
public class ResponseDeserializer extends StdDeserializer<Response> {
private static final long serialVersionUID = -6665611685508708642L;
private static final long MAX_PACKAGE_NUM = 1000;
private ObjectMapper objectMapper = new ObjectMapper();
public ResponseDeserializer() {
this(null);
}
public ResponseDeserializer(Class<?> vc) {
super(vc);
}
@Override
public Response deserialize(JsonParser parser, DeserializationContext ctx)
throws IOException {
final JsonNode node = parser.getCodec().readTree(parser);
final String message = node.get("message").asText();
final List<Package> packageList = new ArrayList<>();
for (var key = 1; key < MAX_PACKAGE_NUM; key ) {
var packageNode = node.get(String.valueOf(key));
if (null == packageNode) {
break;
}
var currentPackage = objectMapper.treeToValue(packageNode, Package.class);
packageList.add(currentPackage);
}
final var response = new Response();
response.setMessage(message);
response.setPackages(packageList.toArray(new Package[0]));
return response;
}
}
類TestDeserializer（示例）：
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
public class TestDeserializer {
public static void main(String[] args) throws JsonMappingException, JsonProcessingException {
String responseJSON = """
{
"message" : "message",
"1": {
"packageCode": "packageCode1",
"packageNum": "packageNum1"
},
"2": {
"packageCode": "packageCode2",
"packageNum": "packageNum2"
}
}
""";
Response response = new ObjectMapper().readValue(responseJSON, Response.class);
System.out.println(response.toString());
}
}
uj5u.com熱心網友回復：
能夠使用自定義解串器解決。
package com.test.json;
import java.io.IOException;
import java.util.ArrayList;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.deser.std.StdDeserializer;
public class TestJsonObjectDeserializer extends StdDeserializer<TestJsonObject> {
private static final long serialVersionUID = 1L;
public TestJsonObjectDeserializer() {
this(null);
}
protected TestJsonObjectDeserializer(Class<?> vc) {
super(vc);
}
@Override
public TestJsonObject deserialize(JsonParser jsonParser, DeserializationContext arg1) throws IOException, JsonProcessingException {
TestJsonObject testJsonObject = new TestJsonObject();
JsonNode jsonNode = jsonParser.getCodec().readTree(jsonParser);
String message = jsonNode.get("message").textValue();
ArrayList<Package> packages = new ArrayList<Package>();
if (message != null) {
testJsonObject.setMessage(message);
int i = 1;
Package package1 = null;
do {
package1 = null;
JsonNode pkg = null;
if (jsonNode.get(String.valueOf(i)) != null) {
pkg = jsonNode.get(String.valueOf(i));
String packageCode = pkg.get("packageCode").textValue();
String packageNum = pkg.get("packageNum").textValue();
package1 = new Package();
package1.setPackageCode(packageCode);
package1.setPackageNum(packageNum);
}
i ;
if (package1 != null) {
packages.add(package1);
}
} while (package1 != null);
if (!packages.isEmpty()) {
Package[] packages1 = new Package[packages.size()];
testJsonObject.setPackages(packages.toArray(packages1));
}
return testJsonObject;
}
return null;
}
}
這里是物件：Package.java
package com.test.json;
public class Package {
protected String packageCode;
protected String packageNum;
public String getPackageCode() {
return packageCode;
}
public void setPackageCode(String packageCode) {
this.packageCode = packageCode;
}
public String getPackageNum() {
return packageNum;
}
public void setPackageNum(String packageNum) {
this.packageNum = packageNum;
}
@Override
public String toString() {
return "Package [packageCode=" packageCode ", packageNum=" packageNum "]";
}
}
TestJson 物件：
package com.test.json;
import java.util.Arrays;
public class TestJsonObject {
protected String message;
protected Package[] packages;
public String getMessage() {
return message;
}
@Override
public String toString() {
return "TestJsonObject [message=" message ", packages=" Arrays.toString(packages) "]";
}
public void setMessage(String message) {
this.message = message;
}
public Package[] getPackages() {
return packages;
}
public void setPackages(Package[] packages) {
this.packages = packages;
}
}
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