要求是为输入 JSON 对象创建一个通用的扁平化实用程序以扁平化 JSON 对象。示例 JSON 如下所示{ "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 }}我一直在尝试将其扁平化为 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，事情变得复杂。此外，我无法理解如何维护嵌套键的唯一性。任何帮助是极大的赞赏。
4 回答
慕哥9229398
TA贡献1877条经验 获得超6个赞
为了避免与键名称冲突，您可以使用JSON 指针规范来创建它们。它也受到Jackson库的支持，因此您可以稍后使用它们来遍历JsonNode节点。
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);
}
}
}
上面的代码打印：
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
阿波罗的战车
TA贡献1862条经验 获得超6个赞
试试这个代码：
public static void flattenJson(JsonNode node, String parent, Map<String, ValueNode> map) {
if (node instanceof ValueNode) {
map.put(parent, (ValueNode)node);
} else {
String prefix = parent == null ? "" : parent + ".";
if (node instanceof ArrayNode) {
ArrayNode arrayNode = (ArrayNode)node;
for(int i = 0; i < arrayNode.size(); i++) {
flattenJson(arrayNode.get(i), prefix + i, map);
}
} else if (node instanceof ObjectNode) {
ObjectNode objectNode = (ObjectNode) node;
for (Iterator<Map.Entry<String, JsonNode>> it = objectNode.fields(); it.hasNext(); ) {
Map.Entry<String, JsonNode> field = it.next();
flattenJson(field.getValue(), prefix + field.getKey(), map);
}
} else {
throw new RuntimeException("unknown json node");
}
}
}
public static Map<String, ValueNode> flattenJson(JsonNode input) {
Map<String, ValueNode> map = new LinkedHashMap<>();
flattenJson(input, null, map);
return map;
}
然后你可以打电话
ObjectMapper om = new ObjectMapper();
JsonNode jsonNode = om.readTree(json);
Map<String, ValueNode> m = flattenJson(jsonNode);
for (Map.Entry<String, ValueNode> kv : m.entrySet()) {
System.out.println(kv.getKey() + "=" + kv.getValue().asText());
}
输出：
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
墨色风雨
TA贡献1853条经验 获得超6个赞
只需将每个级别的键附加到更高级别的键中即可创建键的命名空间。换句话说，你的扁平 JSON 的键将是：
{
"L1key::L2key": "L2val",
"L1key": "L1val",
"L1key::L2key::L3key": "L3val"
}
这样你就可以保证唯一性，而且你也可以从中创建原始的 json。最后确保级别分隔符（此处::）不会出现在您的密钥中。
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