用jackson比较两个JSON对象

阳光穿透心脏的1/2处 2022-11-13 11:26 247阅读 0赞

# 1.概述 #

将使用Jackson-Java的JSON处理库，比较两个JSON对象。

# 2.使用Jackson比较两个JSON对象 #

## 2.1比较两个简单的JSON对象 ##

从使用JsonNode.equals方法开始。 equals()方法执行完整（深度）比较。

假设我们有一个定义为s1变量的JSON字符串：

json字符串1

{ 
        "employee":
        { 
            "id": "1212",
            "fullName": "John Miles",
            "age": 34
        }
    }

json字符串2

{    
        "employee":
        { 
            "id": "1212",
            "age": 34,
            "fullName": "John Miles"
        }
    }

rivate static void test1() throws JsonProcessingException { 
            String json1 = "{ \"employee\": { \"id\": \"1212\", \"fullName\": \"John Miles\", \"age\": 34 }}";
            String json2 = "{ \"employee\": { \"id\": \"1212\", \"age\": 34, \"fullName\": \"John Miles\" }}";
            ObjectMapper objectMapper = new ObjectMapper();
            JsonNode jsonNode1 = objectMapper.readTree(json1);
            JsonNode jsonNode2 = objectMapper.readTree(json2);
            System.out.println(jsonNode1.equals(jsonNode2));//true

**重要的是要注意，即使输入JSON变量json1和josn2中的属性顺序不相同，equals()方法也会忽略顺序并将它们视为相等。**

## 2.2比较带有嵌套元素的两个JSON对象 ##

json1

{  
        "employee":
        { 
            "id": "1212",
            "fullName":"John Miles",
            "age": 34,
            "contact":
            { 
                "email": "john@xyz.com",
                "phone": "9999999999"
            }
        }
    }

json2

{ 
        "employee":
        { 
            "id": "1212",
            "age": 34,
            "fullName": "John Miles",
            "contact":
            { 
                "email": "john@xyz.com",
                "phone": "9999999999"
            }
        }
    }

String json1 = "{ \"employee\": { \"id\": \"1212\", \"fullName\":\"John Miles\", \"age\": 34, \"contact\": { \"email\": \"john@xyz.com\", \"phone\": \"9999999999\" } }}";
            String json2 = "{\"employee\": { \"id\": \"1212\", \"age\": 34, \"fullName\": \"John Miles\", \"contact\": { \"email\": \"john@xyz.com\", \"phone\": \"9999999999\" } }}";
            ObjectMapper objectMapper = new ObjectMapper();
            JsonNode jsonNode1 = objectMapper.readTree(json1);
            JsonNode jsonNode2 = objectMapper.readTree(json2);
            System.out.println(jsonNode1.equals(jsonNode2));//true

同样，应该注意到equals()也可以将两个输入的JSON对象与嵌套元素进行比较。

## 2.3比较两个包含列表元素的JSON对象 ##

json1

{ 
        "employee":
        { 
            "id": "1212",
            "fullName": "John Miles",
            "age": 34,
            "skills": ["Java", "C++", "Python"]
        }
    }

{ 
        "employee":
        { 
            "id": "1212",
            "age": 34,
            "fullName": "John Miles",
            "skills": ["Java", "C++", "Python"] 
        } 
    }

String json1 = "{\"employee\":{\"id\":\"1212\",\"fullName\":\"John Miles\",\"age\":34,\"skills\":[\"Java\",\"C++\",\"Python\"]}}";
            String json2 = "{\"employee\":{\"id\":\"1212\",\"age\":34,\"fullName\":\"John Miles\",\"skills\":[\"Java\",\"C++\",\"Python\"]}}";
            ObjectMapper objectMapper = new ObjectMapper();
            JsonNode jsonNode1 = objectMapper.readTree(json1);
            JsonNode jsonNode2 = objectMapper.readTree(json2);
            System.out.println(jsonNode1.equals(jsonNode2));//true

重要的是要知道，两个列表元素只有在具有完全相同顺序的相同值时才被比较为相等。

# 3.使用自定义比较器比较两个JSON对象 #

在大多数情况下，JsonNode.equals都可以很好地工作。 Jackson还提供JsonNode.equals（comparator，JsonNode）来配置自定义Java Comparator对象。了解如何使用自定义比较器。

## 3.1自定义比较器以比较数值 ##

json1

{ 
        "name": "John",
        "score": 5.0
    }

json2

{ 
        "name": "John",
        "score": 5
    }

String json1 = "{\"name\":\"John\",\"score\":5.0}";
    String json2 = "{\"name\":\"John\",\"score\":5}";
    ObjectMapper objectMapper = new ObjectMapper();
    JsonNode jsonNode1 = objectMapper.readTree(json1);
    JsonNode jsonNode2 = objectMapper.readTree(json2);
    System.out.println(jsonNode1.equals(jsonNode2));//false

首先，创建一个Comparator来比较两个NumericNode对象：

/** * @author Created by niugang on 2021-03-26 17:47 */
    public class NumericNodeComparator implements Comparator<JsonNode>
    { 
        @Override
        public int compare(JsonNode o1, JsonNode o2)
        { 
            if (o1.equals(o2)){ 
                return 0;
            }
            if ((o1 instanceof NumericNode) && (o2 instanceof NumericNode)){ 
                Double d1 = o1.asDouble();
                Double d2 = o2.asDouble();
                if (d1.compareTo(d2) == 0) { 
                    return 0;
                }
            }
            return 1;
        }
    }

String json1 = "{\"name\":\"John\",\"score\":5.0}";
    String json2 = "{\"name\":\"John\",\"score\":5}";
    ObjectMapper objectMapper = new ObjectMapper();
    JsonNode jsonNode1 = objectMapper.readTree(json1);
    JsonNode jsonNode2 = objectMapper.readTree(json2);
    NumericNodeComparator cmp = new NumericNodeComparator();
    System.out.println(jsonNode1.equals(cmp,jsonNode2));//true

## 3.2自定义比较器以比较文本值 ##

json1

{ 
        "name": "john", 
        "score": 5 
    }

json2

{  
        "name": "JOHN", 
        "score": 5 
    }

String json1 = "{\"name\":\"john\",\"score\":5}";
    String json2 = "{\"name\":\"JOHN\",\"score\":5}";
    ObjectMapper objectMapper = new ObjectMapper();
    JsonNode jsonNode1 = objectMapper.readTree(json1);
    JsonNode jsonNode2 = objectMapper.readTree(json2);
    System.out.println(jsonNode1.equals(jsonNode2));//false

创建一个Comparator来比较两个TextNode对象：

public class TextNodeComparator implements Comparator<JsonNode>
    { 
        @Override
        public int compare(JsonNode o1, JsonNode o2) { 
            if (o1.equals(o2)) { 
                return 0;
            }
            if ((o1 instanceof TextNode) && (o2 instanceof TextNode)) { 
                String s1 = o1.asText();
                String s2 = o2.asText();
                if (s1.equalsIgnoreCase(s2)) { 
                    return 0;
                }
            }
            return 1;
        }
    }

private static void test5() throws JsonProcessingException { 
    String json1 = "{\"name\":\"john\",\"score\":5}";
    String json2 = "{\"name\":\"JOHN\",\"score\":5}";
    ObjectMapper objectMapper = new ObjectMapper();
    JsonNode jsonNode1 = objectMapper.readTree(json1);
    JsonNode jsonNode2 = objectMapper.readTree(json2);
    TextNodeComparator textNodeComparator = new TextNodeComparator();
    
    System.out.println(jsonNode1.equals(textNodeComparator,jsonNode2));//true
    }