Antlr4解析Json

àì夳堔傛蜴生んèń 2024-04-18 09:59 59阅读 0赞

项目代码:  [https://download.csdn.net/download/sjhuangx/11868689][https_download.csdn.net_download_sjhuangx_11868689]

# #

## Antlr4的json语法如下： ##

/**
     * Json parser
     */
    grammar Json;
    
    json    : object
            | array
            ;
    
    object
            : '{' pair (',' pair)* '}'  # AnObject
            | '{' '}'                   # EmptyObject // 空对象
            ;
    
    array : '[' value (',' value)* ']'  # ArrayOfValues
          | '[' ']'                     # EmptyArray // 空数组
          ;
    
    pair    : STRING ':' value;
    
    value   : STRING  # String
            | NUMBER  # Atom
            | object  # ObjectValue  // 对象递归调用
            | array   # ArrayValue  // 数组递归调用
            | 'true'  # Atom  // 关键字
            | 'false' # Atom
            | 'null'  # Atom
            ;
    
    // JSON 字符串定义
    STRING  : '"' (ESC | ~["\\])* '"';
    
    fragment ESC     : '\\' (["\\/bfnrt] | UNICODE) ;
    fragment UNICODE : 'u' HEX HEX HEX HEX ;
    fragment HEX     : [0-9a-fA-F] ;
    
    // JSON 数字定义
    NUMBER  : '-'? INT '.' INT EXP?  // 1.35, 1.35E-9, 0.3, -4.5
            | '-'? INT EXP          // 1e10, -3e4
            | '-'? INT              // -3, 45
            ;
    fragment INT : '0' | [1-9] [0-9]* ; // 除0外的数字不允许0开始
    fragment EXP :  [Ee] [+\-]? INT ; // \-是对-的转义, 因为[...] 中的-用于表达"范围"语义
    
    
    // JSON 空白字符定义
    WS : [ \t\n\r]+ -> skip;

## JsonNode节点的定义如下 ##

package json.bean;
    
    public abstract class JsonNode {
    
        public boolean isObject() {
            return false;
        }
    
        public boolean isArray() {
            return false;
        }
    
        public boolean isBool() {
            return false;
        }
    
        public boolean isString() {
            return false;
        }
    
        public boolean isInt() {
            return false;
        }
    
        public boolean isDouble() {
            return false;
        }
    
        public boolean isNull() {
            return false;
        }
    
        public abstract NodeType getNodeType();
    }

### ObjectNode 定义如下： ###

package json.bean;
    
    import java.util.LinkedHashMap;
    import java.util.Map;
    
    public class ObjectNode extends JsonNode {
    
        private Map<String, JsonNode> _children;
    
        public ObjectNode() {
            _children = new LinkedHashMap<>();
        }
    
        @Override
        public boolean isObject() {
            return true;
        }
    
        @Override
        public NodeType getNodeType() {
            return null;
        }
    
        public JsonNode get(String key) {
            return _children.get(key);
        }
    
        public void set(String key, JsonNode value) {
            _children.put(key, value);
        }
    
        @Override
        public String toString() {
            StringBuilder buf = new StringBuilder();
            buf.append('{');
            _children.forEach((k, v) -> buf.append(k).append(": ").append(v).append(","));
            if (!_children.isEmpty()) {
                buf.deleteCharAt(buf.length() - 1);
            }
            buf.append('}');
            return buf.toString();
        }
    }

## ArrayNode定义如下： ##

package json.bean;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class ArrayNode extends JsonNode {
    
        private final List<JsonNode> _children;
    
        public ArrayNode() {
            _children = new ArrayList<>();
        }
    
        @Override
        public boolean isArray() {
            return true;
        }
    
        @Override
        public NodeType getNodeType() {
            return null;
        }
    
        public JsonNode get(int index) {
            return _children.get(index);
        }
    
        public void add(JsonNode value) {
            _children.add(value);
        }
    
        @Override
        public String toString() {
            StringBuilder buf = new StringBuilder();
            buf.append('[');
            if (!_children.isEmpty()) {
                buf.append(_children.get(0));
            }
            for (int i = 1; i < _children.size(); i++) {
                buf.append(",").append(_children.get(i));
            }
            buf.append("]");
            return buf.toString();
        }
    }

## NodeType定义如下： ##

package json.bean;
    
    public enum  NodeType {
    
        BOOL,
        OBJECT,
        ARRAY,
        STRING,
        INT,
        DOUBLE,
        NULL;
    
        private NodeType() {
    
        }
    }

## StringNode定义如下： ##

package json.bean;
    
    public class StringNode extends JsonNode {
    
        private String value;
    
        public StringNode() {
        }
    
        public StringNode(String value) {
            this.value = value;
        }
    
        @Override
        public boolean isString() {
            return true;
        }
    
        @Override
        public NodeType getNodeType() {
            return NodeType.STRING;
        }
    
        public String getValue() {
            return value;
        }
    
        public void setValue(String value) {
            this.value = value;
        }
    
        @Override
        public String toString() {
            return value;
        }
    }

## IntNode定义如下： ##

package json.bean;
    
    public class IntNode extends JsonNode {
    
        private int value;
    
        public IntNode() {
    
        }
    
        public IntNode(int value) {
            this.value = value;
        }
    
        @Override
        public boolean isInt() {
            return true;
        }
    
        @Override
        public NodeType getNodeType() {
            return NodeType.INT;
        }
    
        public int getValue() {
            return value;
        }
    
        public void setValue(int value) {
            this.value = value;
        }
    
        @Override
        public String toString() {
            return Integer.toString(value);
        }
    }

### JsonNodeFactory 是一个用于生成json节点的工具类，内容如下 ###

package json.bean;
    
    public class JsonNodeFactory {
    
        public ObjectNode objectNode() {
            return new ObjectNode();
        }
    
        public ArrayNode arrayNode() {
            return new ArrayNode();
        }
    
        public BoolNode boolNode(boolean value) {
            return BoolNode.valueOf(value);
        }
    
        public IntNode intNode() {
            return new IntNode();
        }
    
        public IntNode intNode(int value) {
            return new IntNode(value);
        }
    
        public DoubleNode doubleNode() {
            return new DoubleNode();
        }
    
        public DoubleNode doubleNode(double value) {
            return new DoubleNode(value);
        }
    
        public NullNode nullNode() {
            return NullNode.getInstance();
        }
    
        public StringNode stringNode() {
            return new StringNode();
        }
    
        public StringNode stringNode(String value) {
            return new StringNode(value);
        }
    }

### 使用Visitor解析并构造Json，定义如下： ###

package json;
    
    import json.bean.ArrayNode;
    import json.bean.JsonNode;
    import json.bean.JsonNodeFactory;
    import json.bean.ObjectNode;
    
    public class MyJsonVisitor extends JsonBaseVisitor<JsonNode> {
    
        public JsonNode jsonNode;
        private JsonNodeFactory nodeFactory;
    
        public MyJsonVisitor() {
            jsonNode = null;
            nodeFactory = new JsonNodeFactory();
        }
    
        @Override
        public JsonNode visitJson(JsonParser.JsonContext ctx) {
            if (ctx.object() != null) {
                jsonNode = visit(ctx.object());
            } else if (ctx.array() != null) {
                 jsonNode = visit(ctx.array());
            }
            return jsonNode;
        }
    
        @Override
        public JsonNode visitAnObject(JsonParser.AnObjectContext ctx) {
            ObjectNode objectNode = nodeFactory.objectNode();
            for (JsonParser.PairContext pairContext : ctx.pair()) {
                JsonNode value = visit(pairContext.value());
                objectNode.set(pairContext.STRING().getText(), value);
            }
            return objectNode;
        }
    
        @Override
        public JsonNode visitEmptyObject(JsonParser.EmptyObjectContext ctx) {
            return nodeFactory.objectNode();
        }
    
        @Override
        public JsonNode visitArrayOfValues(JsonParser.ArrayOfValuesContext ctx) {
            ArrayNode arrayNode = nodeFactory.arrayNode();
            for (JsonParser.ValueContext valueContext : ctx.value()) {
                JsonNode value = visit(valueContext);
                arrayNode.add(value);
            }
            return arrayNode;
        }
    
        @Override
        public JsonNode visitEmptyArray(JsonParser.EmptyArrayContext ctx) {
            return nodeFactory.arrayNode();
        }
    
        @Override
        public JsonNode visitPair(JsonParser.PairContext ctx) {
            return super.visitPair(ctx);
        }
    
        @Override
        public JsonNode visitString(JsonParser.StringContext ctx) {
            return nodeFactory.stringNode(ctx.getText());
        }
    
        @Override
        public JsonNode visitAtom(JsonParser.AtomContext ctx) {
            if (ctx.NUMBER() != null) {
                String text = ctx.NUMBER().getText();
                try {
                    int value = Integer.parseInt(text);
                    return nodeFactory.intNode(value);
                } catch (Exception ignored) {
                }
                double value = Double.parseDouble(ctx.NUMBER().getText());
                return nodeFactory.doubleNode(value);
            } else if (ctx.getText().equals("true")) {
                return nodeFactory.boolNode(true);
            } else if (ctx.getText().equals("false")) {
                return nodeFactory.boolNode(false);
            } else {
                return nodeFactory.nullNode();
            }
        }
    
        @Override
        public JsonNode visitObjectValue(JsonParser.ObjectValueContext ctx) {
            return super.visitObjectValue(ctx);
        }
    
        @Override
        public JsonNode visitArrayValue(JsonParser.ArrayValueContext ctx) {
            return super.visitArrayValue(ctx);
        }
    }

### Json测试内容 ###

{
      "a": "b",
      "c": [1,2,3],
      "d": {
        "name": "test",
        "age": 19,
        "email": "test@email.com"
      },
      "attrs": [{
        "key": "name",
        "type": "string"
      }, {
        "key": "age",
        "type": "int"
      }, {
        "key": "email",
        "type": "string"
      }]
    }

输出如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NqaHVhbmd4_size_16_color_FFFFFF_t_70][]

[https_download.csdn.net_download_sjhuangx_11868689]: https://download.csdn.net/download/sjhuangx/11868689
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NqaHVhbmd4_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20190904215152401.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NqaHVhbmd4,size_16,color_FFFFFF,t_70