问题

今天在 Hive 中 get_json_object 函数解析 json 串的时候，发现函数不支持解析 json 中文 key。
例如：

select get_json_object('{ "姓名":"张三" , "年龄":"18" }', '$.姓名');

我们希望的结果是得到姓名对应的值张三，而运行之后的结果为 NULL 值。

select get_json_object('{ "abc姓名":"张三" , "abc":"18" }', '$.abc姓名');

我们希望的结果是得到姓名对应的值张三，而运行之后的结果为 18 。

产生问题的原因

是什么原因导致的呢？我们查看 Hive 官网中 get_json_object 函数的介绍，可以发现 get_json_object 函数不能解析 json 里面中文的 key，如下图所示：
在这里插入图片描述
json 路径只能包含字符 [0-9a-z_]，即不能包含 大写或特殊字符 。此外，键不能以数字开头。

那为什么 json 路径只能包含字符 [0-9a-z_] 呢？

通过查看源码我们发现 get_json_object 对应的 UDF 类的源码如下：

import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;import com.fasterxml.jackson.core.json.JsonReadFeature;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.collect.Iterators;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;/*** UDFJson.*/
@Description(name = "get_json_object",value = "_FUNC_(json_txt, path) - Extract a json object from path ",extended = "Extract json object from a json string based on json path "+ "specified, and return json string of the extracted json object. It "+ "will return null if the input json string is invalid.\n"+ "A limited version of JSONPath supported:\n"+ "  $   : Root object\n"+ "  .   : Child operator\n"+ "  []  : Subscript operator for array\n"+ "  *   : Wildcard for []\n"+ "Syntax not supported that's worth noticing:\n"+ "  ''  : Zero length string as key\n"+ "  ..  : Recursive descent\n"+ "  &amp;#064;   : Current object/element\n"+ "  ()  : Script expression\n"+ "  ?() : Filter (script) expression.\n"+ "  [,] : Union operator\n"+ "  [start:end:step] : array slice operator\n")//定义了一个名为UDFJson的类，继承自UDF类。
public class UDFGetJsonObjectCN extends UDF {//定义一个静态正则表达式模式，用于匹配JSON路径中的键。//匹配英文key:匹配一个或多个大写字母、小写字母、数字、下划线、连字符、冒号或空格。private static final Pattern patternKey = Pattern.compile("^([a-zA-Z0-9_\\-\\:\\s]+).*");//定义一个静态正则表达式模式，用于匹配JSON路径中的索引。private static final Pattern patternIndex = Pattern.compile("\\[([0-9]+|\\*)\\]");//创建一个ObjectMapper对象，用于解析JSON字符串。private static final ObjectMapper objectMapper = new ObjectMapper();//创建一个JavaType对象，用于表示Map类型。private static final JavaType MAP_TYPE = objectMapper.getTypeFactory().constructType(Map.class);//创建一个JavaType对象，用于表示List类型。private static final JavaType LIST_TYPE = objectMapper.getTypeFactory().constructType(List.class);//静态代码块，用于配置ObjectMapper的一些特性。static {// Allows for unescaped ASCII control characters in JSON valuesobjectMapper.enable(JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS.mappedFeature());// Enabled to accept quoting of all character backslash qooting mechanismobjectMapper.enable(JsonReadFeature.ALLOW_BACKSLASH_ESCAPING_ANY_CHARACTER.mappedFeature());}// An LRU cache using a linked hash map//定义了一个静态内部类HashCache，用作LRU缓存。static class HashCache<K, V> extends LinkedHashMap<K, V> {private static final int CACHE_SIZE = 16;private static final int INIT_SIZE = 32;private static final float LOAD_FACTOR = 0.6f;HashCache() {super(INIT_SIZE, LOAD_FACTOR);}private static final long serialVersionUID = 1;@Overrideprotected boolean removeEldestEntry(Map.Entry<K, V> eldest) {return size() > CACHE_SIZE;}}//声明了一个名为extractObjectCache的HashMap对象，用于缓存已提取的JSON对象。Map<String, Object> extractObjectCache = new HashCache<String, Object>();//声明了一个名为pathExprCache的HashMap对象，用于缓存已解析的JSON路径表达式。Map<String, String[]> pathExprCache = new HashCache<String, String[]>();//声明了一个名为indexListCache的HashMap对象，用于缓存已解析的JSON路径中的索引列表。Map<String, ArrayList<String>> indexListCache =new HashCache<String, ArrayList<String>>();//声明了一个名为mKeyGroup1Cache的HashMap对象，用于缓存JSON路径中的键。Map<String, String> mKeyGroup1Cache = new HashCache<String, String>();//声明了一个名为mKeyMatchesCache的HashMap对象，用于缓存JSON路径中的键是否匹配的结果。Map<String, Boolean> mKeyMatchesCache = new HashCache<String, Boolean>();//构造函数，没有参数。public UDFGetJsonObjectCN() {}/*** Extract json object from a json string based on json path specified, and* return json string of the extracted json object. It will return null if the* input json string is invalid.** A limited version of JSONPath supported: $ : Root object . : Child operator* [] : Subscript operator for array * : Wildcard for []** Syntax not supported that's worth noticing: '' : Zero length string as key* .. : Recursive descent &amp;#064; : Current object/element () : Script* expression ?() : Filter (script) expression. [,] : Union operator* [start:end:step] : array slice operator** @param jsonString*          the json string.* @param pathString*          the json path expression.* @return json string or null when an error happens.*///evaluate方法，用于提取指定路径的JSON对象并返回JSON字符串。public Text evaluate(String jsonString, String pathString) {if (jsonString == null || jsonString.isEmpty() || pathString == null|| pathString.isEmpty() || pathString.charAt(0) != '$') {return null;}int pathExprStart = 1;boolean unknownType = pathString.equals("$");boolean isRootArray = false;if (pathString.length() > 1) {if (pathString.charAt(1) == '[') {pathExprStart = 0;isRootArray = true;} else if (pathString.charAt(1) == '.') {isRootArray = pathString.length() > 2 && pathString.charAt(2) == '[';} else {return null;}}// Cache pathExprString[] pathExpr = pathExprCache.get(pathString);if (pathExpr == null) {pathExpr = pathString.split("\\.", -1);pathExprCache.put(pathString, pathExpr);}// Cache extractObjectObject extractObject = extractObjectCache.get(jsonString);if (extractObject == null) {if (unknownType) {try {extractObject = objectMapper.readValue(jsonString, LIST_TYPE);} catch (Exception e) {// Ignore exception}if (extractObject == null) {try {extractObject = objectMapper.readValue(jsonString, MAP_TYPE);} catch (Exception e) {return null;}}} else {JavaType javaType = isRootArray ? LIST_TYPE : MAP_TYPE;try {extractObject = objectMapper.readValue(jsonString, javaType);} catch (Exception e) {return null;}}extractObjectCache.put(jsonString, extractObject);}for (int i = pathExprStart; i < pathExpr.length; i++) {if (extractObject == null) {return null;}extractObject = extract(extractObject, pathExpr[i], i == pathExprStart && isRootArray);}Text result = new Text();if (extractObject instanceof Map || extractObject instanceof List) {try {result.set(objectMapper.writeValueAsString(extractObject));} catch (Exception e) {return null;}} else if (extractObject != null) {result.set(extractObject.toString());} else {return null;}return result;}//extract方法，递归地提取JSON对象。private Object extract(Object json, String path, boolean skipMapProc) {// skip MAP processing for the first path element if root is arrayif (!skipMapProc) {// Cache patternkey.matcher(path).matches()Matcher mKey = null;Boolean mKeyMatches = mKeyMatchesCache.get(path);if (mKeyMatches == null) {mKey = patternKey.matcher(path);mKeyMatches = mKey.matches() ? Boolean.TRUE : Boolean.FALSE;mKeyMatchesCache.put(path, mKeyMatches);}if (!mKeyMatches.booleanValue()) {return null;}// Cache mkey.group(1)String mKeyGroup1 = mKeyGroup1Cache.get(path);if (mKeyGroup1 == null) {if (mKey == null) {mKey = patternKey.matcher(path);mKeyMatches = mKey.matches() ? Boolean.TRUE : Boolean.FALSE;mKeyMatchesCache.put(path, mKeyMatches);if (!mKeyMatches.booleanValue()) {return null;}}mKeyGroup1 = mKey.group(1);mKeyGroup1Cache.put(path, mKeyGroup1);}json = extract_json_withkey(json, mKeyGroup1);}// Cache indexListArrayList<String> indexList = indexListCache.get(path);if (indexList == null) {Matcher mIndex = patternIndex.matcher(path);indexList = new ArrayList<String>();while (mIndex.find()) {indexList.add(mIndex.group(1));}indexListCache.put(path, indexList);}if (indexList.size() > 0) {json = extract_json_withindex(json, indexList);}return json;}//创建一个名为jsonList的AddingList对象，用于存储提取出来的JSON对象。private transient AddingList jsonList = new AddingList();//定义了一个静态内部类AddingList，继承自ArrayList<Object>，用于添加JSON对象到jsonList中。private static class AddingList extends ArrayList<Object> {private static final long serialVersionUID = 1L;@Overridepublic Iterator<Object> iterator() {return Iterators.forArray(toArray());}@Overridepublic void removeRange(int fromIndex, int toIndex) {super.removeRange(fromIndex, toIndex);}};//extract_json_withindex方法，根据JSON路径中的索引提取JSON对象。@SuppressWarnings("unchecked")private Object extract_json_withindex(Object json, ArrayList<String> indexList) {jsonList.clear();jsonList.add(json);for (String index : indexList) {int targets = jsonList.size();if (index.equalsIgnoreCase("*")) {for (Object array : jsonList) {if (array instanceof List) {for (int j = 0; j < ((List<Object>)array).size(); j++) {jsonList.add(((List<Object>)array).get(j));}}}} else {for (Object array : jsonList) {int indexValue = Integer.parseInt(index);if (!(array instanceof List)) {continue;}List<Object> list = (List<Object>) array;if (indexValue >= list.size()) {continue;}jsonList.add(list.get(indexValue));}}if (jsonList.size() == targets) {return null;}jsonList.removeRange(0, targets);}if (jsonList.isEmpty()) {return null;}return (jsonList.size() > 1) ? new ArrayList<Object>(jsonList) : jsonList.get(0);}//extract_json_withkey方法，根据JSON路径中的键提取JSON对象。@SuppressWarnings("unchecked")private Object extract_json_withkey(Object json, String path) {if (json instanceof List) {List<Object> jsonArray = new ArrayList<Object>();for (int i = 0; i < ((List<Object>) json).size(); i++) {Object json_elem = ((List<Object>) json).get(i);Object json_obj = null;if (json_elem instanceof Map) {json_obj = ((Map<String, Object>) json_elem).get(path);} else {continue;}if (json_obj instanceof List) {for (int j = 0; j < ((List<Object>) json_obj).size(); j++) {jsonArray.add(((List<Object>) json_obj).get(j));}} else if (json_obj != null) {jsonArray.add(json_obj);}}return (jsonArray.size() == 0) ? null : jsonArray;} else if (json instanceof Map) {return ((Map<String, Object>) json).get(path);} else {return null;}}
}

代码做了一些注释，我们可以发现 private final Pattern patternKey = Pattern.compile("^([a-zA-Z0-9_\\-\\:\\s]+).*"); 这个就是匹配 key 的模式串，它的意思是匹配以数字、字母、_、-、:、空格为开头的字符串。那么这个匹配模式串就决定了，get_json_object 函数无法匹配出 key 中带中文的键值对，即select get_json_object('{ "姓名":"张三" , "年龄":"18" }', '$.姓名'); 结果为 null；而 select get_json_object('{ "abc姓名":"张三" , "abc":"18" }', '$.abc姓名'); 中只能匹配以数字、字母、_、-、:、空格为开头的字符串，所以将 abc姓名 中的 abc 当作 key 去取 value 值，所以得到的值为18。

解决办法

知道问题的原因了，那么我们怎么解决这个问题呢，其实很简单，我们只需要修改代码中匹配 key 的正则表达式就可以了。
其实我们可以将 get_json_object 函数的源码拿出来重新写一个 UDF 函数就可以了。

Hive-2.1.1 版本

需要注意自己 Hive 的版本，我们以 Hive-2.1.1 版本为例，代码如下：

package com.yan.hive.udf;import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;import com.google.common.collect.Iterators;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;
import org.codehaus.jackson.JsonFactory;
import org.codehaus.jackson.JsonParser.Feature;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.type.TypeFactory;
import org.codehaus.jackson.type.JavaType;/*** UDFJson.**/
@Description(name = "get_json_object_cn",value = "_FUNC_(json_txt, path) - Extract a json object from path ",extended = "Extract json object from a json string based on json path "+ "specified, and return json string of the extracted json object. It "+ "will return null if the input json string is invalid.\n"+ "A limited version of JSONPath supported:\n"+ "  $   : Root object\n"+ "  .   : Child operator\n"+ "  []  : Subscript operator for array\n"+ "  *   : Wildcard for []\n"+ "Syntax not supported that's worth noticing:\n"+ "  ''  : Zero length string as key\n"+ "  ..  : Recursive descent\n"+ "  &amp;#064;   : Current object/element\n"+ "  ()  : Script expression\n"+ "  ?() : Filter (script) expression.\n"+ "  [,] : Union operator\n"+ "  [start:end:step] : array slice operator\n")
public class UDFGetJsonObjectCN extends UDF {//private final Pattern patternKey = Pattern.compile("^([a-zA-Z0-9_\\-\\:\\s]+).*");private final Pattern patternKey = Pattern.compile("^([^\\[\\]]+).*");private final Pattern patternIndex = Pattern.compile("\\[([0-9]+|\\*)\\]");private static final JsonFactory JSON_FACTORY = new JsonFactory();static {// Allows for unescaped ASCII control characters in JSON valuesJSON_FACTORY.enable(Feature.ALLOW_UNQUOTED_CONTROL_CHARS);// Enabled to accept quoting of all character backslash qooting mechanismJSON_FACTORY.enable(Feature.ALLOW_BACKSLASH_ESCAPING_ANY_CHARACTER);}private static final ObjectMapper MAPPER = new ObjectMapper(JSON_FACTORY);private static final JavaType MAP_TYPE = TypeFactory.fromClass(Map.class);private static final JavaType LIST_TYPE = TypeFactory.fromClass(List.class);// An LRU cache using a linked hash mapstatic class HashCache<K, V> extends LinkedHashMap<K, V> {private static final int CACHE_SIZE = 16;private static final int INIT_SIZE = 32;private static final float LOAD_FACTOR = 0.6f;HashCache() {super(INIT_SIZE, LOAD_FACTOR);}private static final long serialVersionUID = 1;@Overrideprotected boolean removeEldestEntry(Map.Entry<K, V> eldest) {return size() > CACHE_SIZE;}}static Map<String, Object> extractObjectCache = new HashCache<String, Object>();static Map<String, String[]> pathExprCache = new HashCache<String, String[]>();static Map<String, ArrayList<String>> indexListCache =new HashCache<String, ArrayList<String>>();static Map<String, String> mKeyGroup1Cache = new HashCache<String, String>();static Map<String, Boolean> mKeyMatchesCache = new HashCache<String, Boolean>();Text result = new Text();public UDFGetJsonObjectCN() {}/*** Extract json object from a json string based on json path specified, and* return json string of the extracted json object. It will return null if the* input json string is invalid.** A limited version of JSONPath supported: $ : Root object . : Child operator* [] : Subscript operator for array * : Wildcard for []** Syntax not supported that's worth noticing: '' : Zero length string as key* .. : Recursive descent &amp;#064; : Current object/element () : Script* expression ?() : Filter (script) expression. [,] : Union operator* [start:end:step] : array slice operator** @param jsonString*          the json string.* @param pathString*          the json path expression.* @return json string or null when an error happens.*/public Text evaluate(String jsonString, String pathString) {if (jsonString == null || jsonString.isEmpty() || pathString == null|| pathString.isEmpty() || pathString.charAt(0) != '$') {return null;}int pathExprStart = 1;boolean isRootArray = false;if (pathString.length() > 1) {if (pathString.charAt(1) == '[') {pathExprStart = 0;isRootArray = true;} else if (pathString.charAt(1) == '.') {isRootArray = pathString.length() > 2 && pathString.charAt(2) == '[';} else {return null;}}// Cache pathExprString[] pathExpr = pathExprCache.get(pathString);if (pathExpr == null) {pathExpr = pathString.split("\\.", -1);pathExprCache.put(pathString, pathExpr);}// Cache extractObjectObject extractObject = extractObjectCache.get(jsonString);if (extractObject == null) {JavaType javaType = isRootArray ? LIST_TYPE : MAP_TYPE;try {extractObject = MAPPER.readValue(jsonString, javaType);} catch (Exception e) {return null;}extractObjectCache.put(jsonString, extractObject);}for (int i = pathExprStart; i < pathExpr.length; i++) {if (extractObject == null) {return null;}extractObject = extract(extractObject, pathExpr[i], i == pathExprStart && isRootArray);}if (extractObject instanceof Map || extractObject instanceof List) {try {result.set(MAPPER.writeValueAsString(extractObject));} catch (Exception e) {return null;}} else if (extractObject != null) {result.set(extractObject.toString());} else {return null;}return result;}private Object extract(Object json, String path, boolean skipMapProc) {// skip MAP processing for the first path element if root is arrayif (!skipMapProc) {// Cache patternkey.matcher(path).matches()Matcher mKey = null;Boolean mKeyMatches = mKeyMatchesCache.get(path);if (mKeyMatches == null) {mKey = patternKey.matcher(path);mKeyMatches = mKey.matches() ? Boolean.TRUE : Boolean.FALSE;mKeyMatchesCache.put(path, mKeyMatches);}if (!mKeyMatches.booleanValue()) {return null;}// Cache mkey.group(1)String mKeyGroup1 = mKeyGroup1Cache.get(path);if (mKeyGroup1 == null) {if (mKey == null) {mKey = patternKey.matcher(path);mKeyMatches = mKey.matches() ? Boolean.TRUE : Boolean.FALSE;mKeyMatchesCache.put(path, mKeyMatches);if (!mKeyMatches.booleanValue()) {return null;}}mKeyGroup1 = mKey.group(1);mKeyGroup1Cache.put(path, mKeyGroup1);}json = extract_json_withkey(json, mKeyGroup1);}// Cache indexListArrayList<String> indexList = indexListCache.get(path);if (indexList == null) {Matcher mIndex = patternIndex.matcher(path);indexList = new ArrayList<String>();while (mIndex.find()) {indexList.add(mIndex.group(1));}indexListCache.put(path, indexList);}if (indexList.size() > 0) {json = extract_json_withindex(json, indexList);}return json;}private transient AddingList jsonList = new AddingList();private static class AddingList extends ArrayList<Object> {@Overridepublic Iterator<Object> iterator() {return Iterators.forArray(toArray());}@Overridepublic void removeRange(int fromIndex, int toIndex) {super.removeRange(fromIndex, toIndex);}};@SuppressWarnings("unchecked")private Object extract_json_withindex(Object json, ArrayList<String> indexList) {jsonList.clear();jsonList.add(json);for (String index : indexList) {int targets = jsonList.size();if (index.equalsIgnoreCase("*")) {for (Object array : jsonList) {if (array instanceof List) {for (int j = 0; j < ((List<Object>)array).size(); j++) {jsonList.add(((List<Object>)array).get(j));}}}} else {for (Object array : jsonList) {int indexValue = Integer.parseInt(index);if (!(array instanceof List)) {continue;}List<Object> list = (List<Object>) array;if (indexValue >= list.size()) {continue;}jsonList.add(list.get(indexValue));}}if (jsonList.size() == targets) {return null;}jsonList.removeRange(0, targets);}if (jsonList.isEmpty()) {return null;}return (jsonList.size() > 1) ? new ArrayList<Object>(jsonList) : jsonList.get(0);}@SuppressWarnings("unchecked")private Object extract_json_withkey(Object json, String path) {if (json instanceof List) {List<Object> jsonArray = new ArrayList<Object>();for (int i = 0; i < ((List<Object>) json).size(); i++) {Object json_elem = ((List<Object>) json).get(i);Object json_obj = null;if (json_elem instanceof Map) {json_obj = ((Map<String, Object>) json_elem).get(path);} else {continue;}if (json_obj instanceof List) {for (int j = 0; j < ((List<Object>) json_obj).size(); j++) {jsonArray.add(((List<Object>) json_obj).get(j));}} else if (json_obj != null) {jsonArray.add(json_obj);}}return (jsonArray.size() == 0) ? null : jsonArray;} else if (json instanceof Map) {return ((Map<String, Object>) json).get(path);} else {return null;}}
}

需要导入的依赖，要和自己集群的版本契合，Hadoop 的版本及 Hive 的版本。

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.atguigu.hive</groupId><artifactId>hivetest</artifactId><version>1.0-SNAPSHOT</version><properties><hadoop.version>3.0.0</hadoop.version><hive.version>2.1.1</hive.version><jackson.version>1.9.2</jackson.version><guava.version>14.0.1</guava.version></properties><dependencies><dependency><groupId>org.apache.hive</groupId><artifactId>hive-exec</artifactId><version>${hive.version}</version></dependency><!-- https://mvnrepository.com/artifact/org.apache.hive/hive-jdbc --><dependency><groupId>org.apache.hive</groupId><artifactId>hive-jdbc</artifactId><version>${hive.version}</version></dependency><dependency><groupId>org.apache.hadoop</groupId><artifactId>hadoop-common</artifactId><version>${hadoop.version}</version></dependency><dependency><groupId>com.google.guava</groupId><artifactId>guava</artifactId><version>${guava.version}</version></dependency><dependency><groupId>org.codehaus.jackson</groupId><artifactId>jackson-core-asl</artifactId><version>${jackson.version}</version></dependency><dependency><groupId>org.codehaus.jackson</groupId><artifactId>jackson-mapper-asl</artifactId><version>${jackson.version}</version></dependency><dependency><groupId>org.codehaus.jackson</groupId><artifactId>jackson-jaxrs</artifactId><version>${jackson.version}</version></dependency><dependency><groupId>org.codehaus.jackson</groupId><artifactId>jackson-xc</artifactId><version>${jackson.version}</version></dependency></dependencies></project>

注意： 因为上述UDF中也用到了 com.google.guava 和 org.codehaus.jackson，所以这两个依赖要和 hive 版本中所用的依赖版本一致。

Hive-4.0.0 版本

package com.yan.hive.udf;import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;import com.fasterxml.jackson.core.json.JsonReadFeature;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.collect.Iterators;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;/*** @author Yan* @create 2023-08-05 22:21* hive解析json中文key*/
@Description(name = "get_json_object_cn",value = "_FUNC_(json_txt, path) - Extract a json object from path ",extended = "Extract json object from a json string based on json path "+ "specified, and return json string of the extracted json object. It "+ "will return null if the input json string is invalid.\n"+ "A limited version of JSONPath supported:\n"+ "  $   : Root object\n"+ "  .   : Child operator\n"+ "  []  : Subscript operator for array\n"+ "  *   : Wildcard for []\n"+ "Syntax not supported that's worth noticing:\n"+ "  ''  : Zero length string as key\n"+ "  ..  : Recursive descent\n"+ "  &amp;#064;   : Current object/element\n"+ "  ()  : Script expression\n"+ "  ?() : Filter (script) expression.\n"+ "  [,] : Union operator\n"+ "  [start:end:step] : array slice operator\n")//定义了一个名为UDFJson的类，继承自UDF类。
public class UDFGetJsonObjectCN extends UDF {//定义一个静态正则表达式模式，用于匹配JSON路径中的键。//匹配英文key:匹配一个或多个大写字母、小写字母、数字、下划线、连字符、冒号或空格。//private static final Pattern patternKey = Pattern.compile("^([a-zA-Z0-9_\\-\\:\\s]+).*");//可以匹配中文,\\p{L}来匹配任意Unicode字母字符，包括中文字符:英文、数字、下划线、连字符、冒号、空格和中文字符。//private static final Pattern patternKey = Pattern.compile("^([a-zA-Z0-9_\\-\\:\\s\\p{L}]+).*");//可以匹配中文,\\p{L}来匹配任意Unicode字母字符，包括中文字符,但不包含特殊字符,特殊字符需自己添加//private static final Pattern patternKey = Pattern.compile("^([a-zA-Z0-9_\\-\\:\\s?%*+\\p{L}]+).*");//可以匹配中文，包含特殊字符，但不包含英文下的点(.);还有就是匹配不到路径中的索引了//private static final Pattern patternKey = Pattern.compile("^(.+).*");//可以匹配中文，包含特殊字符，不包中括号"[]"，但不包含英文下的点(.);这样就可以匹配路径中的索引了private static final Pattern patternKey = Pattern.compile("^([^\\[\\]]+).*");//定义一个静态正则表达式模式，用于匹配JSON路径中的索引。private static final Pattern patternIndex = Pattern.compile("\\[([0-9]+|\\*)\\]");//创建一个ObjectMapper对象，用于解析JSON字符串。private static final ObjectMapper objectMapper = new ObjectMapper();//创建一个JavaType对象，用于表示Map类型。private static final JavaType MAP_TYPE = objectMapper.getTypeFactory().constructType(Map.class);//创建一个JavaType对象，用于表示List类型。private static final JavaType LIST_TYPE = objectMapper.getTypeFactory().constructType(List.class);//静态代码块，用于配置ObjectMapper的一些特性。static {// Allows for unescaped ASCII control characters in JSON valuesobjectMapper.enable(JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS.mappedFeature());// Enabled to accept quoting of all character backslash qooting mechanismobjectMapper.enable(JsonReadFeature.ALLOW_BACKSLASH_ESCAPING_ANY_CHARACTER.mappedFeature());}// An LRU cache using a linked hash map//定义了一个静态内部类HashCache，用作LRU缓存。static class HashCache<K, V> extends LinkedHashMap<K, V> {private static final int CACHE_SIZE = 16;private static final int INIT_SIZE = 32;private static final float LOAD_FACTOR = 0.6f;HashCache() {super(INIT_SIZE, LOAD_FACTOR);}private static final long serialVersionUID = 1;@Overrideprotected boolean removeEldestEntry(Map.Entry<K, V> eldest) {return size() > CACHE_SIZE;}}//声明了一个名为extractObjectCache的HashMap对象，用于缓存已提取的JSON对象。Map<String, Object> extractObjectCache = new HashCache<String, Object>();//声明了一个名为pathExprCache的HashMap对象，用于缓存已解析的JSON路径表达式。Map<String, String[]> pathExprCache = new HashCache<String, String[]>();//声明了一个名为indexListCache的HashMap对象，用于缓存已解析的JSON路径中的索引列表。Map<String, ArrayList<String>> indexListCache =new HashCache<String, ArrayList<String>>();//声明了一个名为mKeyGroup1Cache的HashMap对象，用于缓存JSON路径中的键。Map<String, String> mKeyGroup1Cache = new HashCache<String, String>();//声明了一个名为mKeyMatchesCache的HashMap对象，用于缓存JSON路径中的键是否匹配的结果。Map<String, Boolean> mKeyMatchesCache = new HashCache<String, Boolean>();//构造函数，没有参数。public UDFGetJsonObjectCN() {}/*** Extract json object from a json string based on json path specified, and* return json string of the extracted json object. It will return null if the* input json string is invalid.** A limited version of JSONPath supported: $ : Root object . : Child operator* [] : Subscript operator for array * : Wildcard for []** Syntax not supported that's worth noticing: '' : Zero length string as key* .. : Recursive descent &amp;#064; : Current object/element () : Script* expression ?() : Filter (script) expression. [,] : Union operator* [start:end:step] : array slice operator** @param jsonString*          the json string.* @param pathString*          the json path expression.* @return json string or null when an error happens.*///evaluate方法，用于提取指定路径的JSON对象并返回JSON字符串。public Text evaluate(String jsonString, String pathString) {if (jsonString == null || jsonString.isEmpty() || pathString == null|| pathString.isEmpty() || pathString.charAt(0) != '$') {return null;}int pathExprStart = 1;boolean unknownType = pathString.equals("$");boolean isRootArray = false;if (pathString.length() > 1) {if (pathString.charAt(1) == '[') {pathExprStart = 0;isRootArray = true;} else if (pathString.charAt(1) == '.') {isRootArray = pathString.length() > 2 && pathString.charAt(2) == '[';} else {return null;}}// Cache pathExprString[] pathExpr = pathExprCache.get(pathString);if (pathExpr == null) {pathExpr = pathString.split("\\.", -1);pathExprCache.put(pathString, pathExpr);}// Cache extractObjectObject extractObject = extractObjectCache.get(jsonString);if (extractObject == null) {if (unknownType) {try {extractObject = objectMapper.readValue(jsonString, LIST_TYPE);} catch (Exception e) {// Ignore exception}if (extractObject == null) {try {extractObject = objectMapper.readValue(jsonString, MAP_TYPE);} catch (Exception e) {return null;}}} else {JavaType javaType = isRootArray ? LIST_TYPE : MAP_TYPE;try {extractObject = objectMapper.readValue(jsonString, javaType);} catch (Exception e) {return null;}}extractObjectCache.put(jsonString, extractObject);}for (int i = pathExprStart; i < pathExpr.length; i++) {if (extractObject == null) {return null;}extractObject = extract(extractObject, pathExpr[i], i == pathExprStart && isRootArray);}Text result = new Text();if (extractObject instanceof Map || extractObject instanceof List) {try {result.set(objectMapper.writeValueAsString(extractObject));} catch (Exception e) {return null;}} else if (extractObject != null) {result.set(extractObject.toString());} else {return null;}return result;}//extract方法，递归地提取JSON对象。private Object extract(Object json, String path, boolean skipMapProc) {// skip MAP processing for the first path element if root is arrayif (!skipMapProc) {// Cache patternkey.matcher(path).matches()Matcher mKey = null;Boolean mKeyMatches = mKeyMatchesCache.get(path);if (mKeyMatches == null) {mKey = patternKey.matcher(path);mKeyMatches = mKey.matches() ? Boolean.TRUE : Boolean.FALSE;mKeyMatchesCache.put(path, mKeyMatches);}if (!mKeyMatches.booleanValue()) {return null;}// Cache mkey.group(1)String mKeyGroup1 = mKeyGroup1Cache.get(path);if (mKeyGroup1 == null) {if (mKey == null) {mKey = patternKey.matcher(path);mKeyMatches = mKey.matches() ? Boolean.TRUE : Boolean.FALSE;mKeyMatchesCache.put(path, mKeyMatches);if (!mKeyMatches.booleanValue()) {return null;}}mKeyGroup1 = mKey.group(1);mKeyGroup1Cache.put(path, mKeyGroup1);}json = extract_json_withkey(json, mKeyGroup1);}// Cache indexListArrayList<String> indexList = indexListCache.get(path);if (indexList == null) {Matcher mIndex = patternIndex.matcher(path);indexList = new ArrayList<String>();while (mIndex.find()) {indexList.add(mIndex.group(1));}indexListCache.put(path, indexList);}if (indexList.size() > 0) {json = extract_json_withindex(json, indexList);}return json;}//创建一个名为jsonList的AddingList对象，用于存储提取出来的JSON对象。private transient AddingList jsonList = new AddingList();//定义了一个静态内部类AddingList，继承自ArrayList<Object>，用于添加JSON对象到jsonList中。private static class AddingList extends ArrayList<Object> {private static final long serialVersionUID = 1L;@Overridepublic Iterator<Object> iterator() {return Iterators.forArray(toArray());}@Overridepublic void removeRange(int fromIndex, int toIndex) {super.removeRange(fromIndex, toIndex);}};//extract_json_withindex方法，根据JSON路径中的索引提取JSON对象。@SuppressWarnings("unchecked")private Object extract_json_withindex(Object json, ArrayList<String> indexList) {jsonList.clear();jsonList.add(json);for (String index : indexList) {int targets = jsonList.size();if (index.equalsIgnoreCase("*")) {for (Object array : jsonList) {if (array instanceof List) {for (int j = 0; j < ((List<Object>)array).size(); j++) {jsonList.add(((List<Object>)array).get(j));}}}} else {for (Object array : jsonList) {int indexValue = Integer.parseInt(index);if (!(array instanceof List)) {continue;}List<Object> list = (List<Object>) array;if (indexValue >= list.size()) {continue;}jsonList.add(list.get(indexValue));}}if (jsonList.size() == targets) {return null;}jsonList.removeRange(0, targets);}if (jsonList.isEmpty()) {return null;}return (jsonList.size() > 1) ? new ArrayList<Object>(jsonList) : jsonList.get(0);}//extract_json_withkey方法，根据JSON路径中的键提取JSON对象。@SuppressWarnings("unchecked")private Object extract_json_withkey(Object json, String path) {if (json instanceof List) {List<Object> jsonArray = new ArrayList<Object>();for (int i = 0; i < ((List<Object>) json).size(); i++) {Object json_elem = ((List<Object>) json).get(i);Object json_obj = null;if (json_elem instanceof Map) {json_obj = ((Map<String, Object>) json_elem).get(path);} else {continue;}if (json_obj instanceof List) {for (int j = 0; j < ((List<Object>) json_obj).size(); j++) {jsonArray.add(((List<Object>) json_obj).get(j));}} else if (json_obj != null) {jsonArray.add(json_obj);}}return (jsonArray.size() == 0) ? null : jsonArray;} else if (json instanceof Map) {return ((Map<String, Object>) json).get(path);} else {return null;}}
}

依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.atguigu.hive</groupId><artifactId>hivetest</artifactId><version>1.0-SNAPSHOT</version><properties><hadoop.version>3.3.1</hadoop.version><hive.version>4.0.0</hive.version><jackson.version>2.13.5</jackson.version><guava.version>22.0</guava.version></properties><dependencies><dependency><groupId>com.fasterxml.jackson</groupId><artifactId>jackson-bom</artifactId><version>${jackson.version}</version><type>pom</type><scope>import</scope></dependency><dependency><groupId>com.google.guava</groupId><artifactId>guava</artifactId><version>${guava.version}</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId><version>${jackson.version}</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>${jackson.version}</version></dependency><dependency><groupId>org.apache.hive</groupId><artifactId>hive-jdbc</artifactId><version>${hive.version}</version></dependency></dependencies></project>