在 Java 中展平 3 级嵌套 JSON 字符串 [英] Flattening a 3 level nested JSON string in java
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问题描述
要求是为输入的 JSON 对象创建一个通用的扁平化实用程序到扁平化的 JSON 对象.
The requirement is to create a generic flattening utility for an input JSON object to a flattened JSON object.
示例 JSON 如下所示
The sample JSON looks like the below
{
"Source": "source-1",
"Rows": [
{
"Keys": {
"device-id": "BC04-EBH-N3K-01",
"interface-name": "TenGigE0/0/0/39",
"node-name": "0/0/CPU0"
},
"Timestamp": 1567621527656,
"inner": {
"donm": {
"id": "0062",
"mol": {
"rem": 30,
"len": 11,
"org": {
"ldp": [
{
"t": 486,
"o": 322
},
{
"t": 487,
"o": 32,
"twss": 1,
"tlv": "00:01"
}
]
},
"chlen": 14,
"poe": 5,
"combs": 10,
"chaype": 4,
"rek": 0,
"rem-um": 67
},
"detail": {
"enas": "B,R",
"systes": "B,R",
"timng": 91,
"syn": "C",
"met-type": 0,
"neses": {
"lldEDIT": [
{
"ium": 830,
"m": 1,
"ass": {
"ape": "ipv4",
"ipvs": "94"
}
}
]
},
"pess": "0008",
"por]d": 0,
"pon": "BCtive",
"sysme": "BC1"
},
"reme": "Bu1",
"hean": 0,
"porl": "Et1"
}
}
}
],
"Tey": {
"epath": "Cgetail",
"sustr": "MX",
"coime": 1567621527653,
"msp": 1567621527653,
"come": 1567621527660,
"nor": "BC5",
"cid": 14789654
}
}
我一直试图将其展平为 3 个级别，并提出了以下实用程序.但是，当我必须处理数组和 String、long、Timestamp 等类型的值时，事情变得越来越复杂.此外，我无法理解如何维护嵌套键的唯一性.
I have been trying to flatten it to 3 levels and came up with the below utility. But, The things are getting complicated when I have to deal with Arrays and values of type String, long, Timestamp, etc. Also, I am unable to understand how the nested keys can be maintained for uniqueness.
public static Map<String,Object> flattenJson(JsonNode input){
Map<String,Object> finalMap = new HashMap<>();
ObjectMapper datamapper = new ObjectMapper();
Map<String,Object> topLevelJsonMap = datamapper.convertValue(input,Map.class);
Set<String> topLevelKeys = topLevelJsonMap.keySet();
for(String topLevelKey : topLevelKeys){
System.out.println("Key :::: "+topLevelKey);
Object topLevelData = topLevelJsonMap.get(topLevelKey);
System.out.println("value :::: "+topLevelData.toString());
if(topLevelData instanceof ArrayNode){
ArrayNode arrayOfData = (ArrayNode) topLevelData;
for(JsonNode dataNode : arrayOfData){
flattenJson(input);
}
} else if(topLevelData instanceof JsonNode){
Map<String,Object> innerLevelJsonMap = datamapper.convertValue(topLevelData,Map.class);
Set<String> innerLevelKeys = innerLevelJsonMap.keySet();
for(String innerLevelKey : innerLevelKeys){
System.out.println("inner key :::: "+innerLevelKey);
flattenJson((JsonNode) innerLevelJsonMap.get(innerLevelKey));
}
}else {
finalMap.put(topLevelKey,topLevelData);
}
}
return finalMap;
}
非常感谢任何帮助.
推荐答案
为了避免与键名冲突，您可以使用 JSON 指针 规范来创建它们.Jackson 库也支持它，因此您可以稍后使用它们来遍历 JsonNode 节点.
To avoid conflicts with key names you can use JSON Pointer specification to create them. It is also supported by Jackson library, so you can use them later to traverse the JsonNode node.
简单的实现如下所示:
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
import java.io.File;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicInteger;
public class JsonApp {
public static void main(String[] args) throws Exception {
File jsonFile = new File("./test.json");
ObjectMapper mapper = new ObjectMapper();
JsonNode root = mapper.readTree(jsonFile);
Map<String, JsonNode> map = new JsonFlattener(root).flatten();
System.out.println("Use key-value pairs:");
map.forEach(
(k, v) -> {
System.out.println(k + " => " + v);
});
System.out.println();
System.out.println("Use pointers:");
map.forEach(
(k, v) -> {
System.out.println(k + " => " + root.at(k));
});
}
}
class JsonFlattener {
private final Map<String, JsonNode> json = new LinkedHashMap<>(64);
private final JsonNode root;
JsonFlattener(JsonNode node) {
this.root = Objects.requireNonNull(node);
}
public Map<String, JsonNode> flatten() {
process(root, "");
return json;
}
private void process(JsonNode node, String prefix) {
if (node.isObject()) {
ObjectNode object = (ObjectNode) node;
object
.fields()
.forEachRemaining(
entry -> {
process(entry.getValue(), prefix + "/" + entry.getKey());
});
} else if (node.isArray()) {
ArrayNode array = (ArrayNode) node;
AtomicInteger counter = new AtomicInteger();
array
.elements()
.forEachRemaining(
item -> {
process(item, prefix + "/" + counter.getAndIncrement());
});
} else {
json.put(prefix, node);
}
}
}
以上代码打印:
Use key-value pairs:
/Source => "source-1"
/Rows/0/Keys/device-id => "BC04-EBH-N3K-01"
/Rows/0/Keys/interface-name => "TenGigE0/0/0/39"
/Rows/0/Keys/node-name => "0/0/CPU0"
/Rows/0/Timestamp => 1567621527656
/Rows/0/inner/donm/id => "0062"
/Rows/0/inner/donm/mol/rem => 30
/Rows/0/inner/donm/mol/len => 11
/Rows/0/inner/donm/mol/org/ldp/0/t => 486
/Rows/0/inner/donm/mol/org/ldp/0/o => 322
/Rows/0/inner/donm/mol/org/ldp/1/t => 487
/Rows/0/inner/donm/mol/org/ldp/1/o => 32
/Rows/0/inner/donm/mol/org/ldp/1/twss => 1
/Rows/0/inner/donm/mol/org/ldp/1/tlv => "00:01"
/Rows/0/inner/donm/mol/chlen => 14
/Rows/0/inner/donm/mol/poe => 5
/Rows/0/inner/donm/mol/combs => 10
/Rows/0/inner/donm/mol/chaype => 4
/Rows/0/inner/donm/mol/rek => 0
/Rows/0/inner/donm/mol/rem-um => 67
/Rows/0/inner/donm/detail/enas => "B,R"
/Rows/0/inner/donm/detail/systes => "B,R"
/Rows/0/inner/donm/detail/timng => 91
/Rows/0/inner/donm/detail/syn => "C"
/Rows/0/inner/donm/detail/met-type => 0
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ium => 830
/Rows/0/inner/donm/detail/neses/lldEDIT/0/m => 1
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ass/ape => "ipv4"
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ass/ipvs => "94"
/Rows/0/inner/donm/detail/pess => "0008"
/Rows/0/inner/donm/detail/por]d => 0
/Rows/0/inner/donm/detail/pon => "BCtive"
/Rows/0/inner/donm/detail/sysme => "BC1"
/Rows/0/inner/donm/reme => "Bu1"
/Rows/0/inner/donm/hean => 0
/Rows/0/inner/donm/porl => "Et1"
/Tey/epath => "Cgetail"
/Tey/sustr => "MX"
/Tey/coime => 1567621527653
/Tey/msp => 1567621527653
/Tey/come => 1567621527660
/Tey/nor => "BC5"
/Tey/cid => 14789654
Use pointers:
/Source => "source-1"
/Rows/0/Keys/device-id => "BC04-EBH-N3K-01"
/Rows/0/Keys/interface-name => "TenGigE0/0/0/39"
/Rows/0/Keys/node-name => "0/0/CPU0"
/Rows/0/Timestamp => 1567621527656
/Rows/0/inner/donm/id => "0062"
/Rows/0/inner/donm/mol/rem => 30
/Rows/0/inner/donm/mol/len => 11
/Rows/0/inner/donm/mol/org/ldp/0/t => 486
/Rows/0/inner/donm/mol/org/ldp/0/o => 322
/Rows/0/inner/donm/mol/org/ldp/1/t => 487
/Rows/0/inner/donm/mol/org/ldp/1/o => 32
/Rows/0/inner/donm/mol/org/ldp/1/twss => 1
/Rows/0/inner/donm/mol/org/ldp/1/tlv => "00:01"
/Rows/0/inner/donm/mol/chlen => 14
/Rows/0/inner/donm/mol/poe => 5
/Rows/0/inner/donm/mol/combs => 10
/Rows/0/inner/donm/mol/chaype => 4
/Rows/0/inner/donm/mol/rek => 0
/Rows/0/inner/donm/mol/rem-um => 67
/Rows/0/inner/donm/detail/enas => "B,R"
/Rows/0/inner/donm/detail/systes => "B,R"
/Rows/0/inner/donm/detail/timng => 91
/Rows/0/inner/donm/detail/syn => "C"
/Rows/0/inner/donm/detail/met-type => 0
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ium => 830
/Rows/0/inner/donm/detail/neses/lldEDIT/0/m => 1
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ass/ape => "ipv4"
/Rows/0/inner/donm/detail/neses/lldEDIT/0/ass/ipvs => "94"
/Rows/0/inner/donm/detail/pess => "0008"
/Rows/0/inner/donm/detail/por]d => 0
/Rows/0/inner/donm/detail/pon => "BCtive"
/Rows/0/inner/donm/detail/sysme => "BC1"
/Rows/0/inner/donm/reme => "Bu1"
/Rows/0/inner/donm/hean => 0
/Rows/0/inner/donm/porl => "Et1"
/Tey/epath => "Cgetail"
/Tey/sustr => "MX"
/Tey/coime => 1567621527653
/Tey/msp => 1567621527653
/Tey/come => 1567621527660
/Tey/nor => "BC5"
/Tey/cid => 14789654
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