使用 Jackson 将布尔值序列化和反序列化为整数

2025年3月17日 | 阅读 7 分钟

在 Java 中，Jackson 库是处理 JSON 时的实际标准。为了将布尔值映射到整数值，Jackson 定义良好的默认值是不够的，为此，我们需要执行手动配置。

在本节中，我们将了解如何将布尔值序列化为整数、数字字符串，反之亦然。

让我们逐一了解序列化和反序列化

序列化

正如我们已经提到的，Jackson 定义良好的默认值不足以将布尔值映射到整数值。因此，我们将执行手动配置，即**字段级别配置**和**全局配置**。让我们逐一了解这两种类型的配置。

字段级别配置

我们可以通过使用 **@JsonFormat** 注释我们的 Boolean 字段来简单地将 Boolean 序列化为 Integer。我们使用 Shape.Number 设置 Shape，如下所示

@JsonFormat(shape = Shape.NUMBER)
private Boolean passed;
@JsonFormat(shape = Shape.NUMBER)
private Boolean fail;

让我们看一个例子来了解如何将布尔值序列化为整数。

SerializeBooleansAsIntegerExample1.java

// import required classes and package if any
import java.util.Scanner;
import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonFormat.Shape;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

// create class SerializeBooleanAsIntegerExample1 to serialize java object by mapping Boolean as Integer
public class SerializeBooleanAsIntegerExample1 {
	
	// main() method start
	public static void main(String args[]) throws JsonProcessingException {
		
		String id, name, status;
		Boolean passed = false, fail = false;
		
		// create an instance of Scanner class
		Scanner sc = new Scanner(System.in);
		
		System.out.println("Enter Student Id: ");
		id = sc.nextLine();
		
		System.out.println("Enter Student Name: ");
		name = sc.nextLine();
		
		System.out.println("Is "+name+ "pass in exams(Yes/No)?: ");
		status = sc.nextLine();
		
		if(status.equals("Yes")) {
			passed = true;
		}
		
		if(status.equals("No")) {
			fail = false;
		}
		
		// close Scanner class object
		sc.close();
		
		// create Student object
		Student std = new Student(id, name, passed, fail);

		// create an instance of ObjectMapper class
	    	ObjectMapper mapper = new ObjectMapper();
	    
	    	//serialize Student object to JSON
	    	String jsonString = mapper.writeValueAsString(std);
	    
	    	System.out.println("Java object after serializing:"+jsonString);
	}
	
}
class Student {

    	private String stdId;
    	private String stdName;
    
    	@JsonFormat(shape = Shape.NUMBER)
    	private Boolean passed;
    
    	@JsonFormat(shape = Shape.NUMBER)
    	private Boolean fail;

    	public Student(String stdId, String stdName, Boolean passed, Boolean fail) {
    		this.stdId = stdId;
    		this.stdName = stdName;
    		this.passed = passed;
    		this.fail = fail;
    	}
    
    	public String getStdId() {
    		return stdId;
    	}
    
    	public String getStdName() {
    		return stdName;
    	}
    
   	public Boolean getPassed() {
    		return passed;
    	}
    
   	public Boolean getFail() {
    		return fail;
    	}
    
}

输出

Serialize and Deserialize Booleans as Integers with Jackson

全局配置

有时，无法注释每个字段。因此，我们使用全局配置的概念来全局配置 Boolean 到 Integer 的序列化。 Jackson 允许我们通过覆盖 ObjectMapper 类中的默认值来全局配置 @JsonFormat 注释。

让我们看一个示例，了解如何通过全局配置 ObjectMapper 类将布尔值序列化为整数。

SerializeBooleanAsIntegerExample2.java

//import required classes and package if any
import java.util.Scanner;
import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonFormat.Shape;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

//create class SerializeBooleanAsIntegerExample2 to serialize java object by mapping Boolean as Integer globally
public class SerializeBooleanAsIntegerExample2 {
	
	// main() method start
	public static void main(String args[]) throws JsonProcessingException {
		
		String id, name, status;
		Boolean passed = false, fail = false;
		
		// create an instance of Scanner class
		Scanner sc = new Scanner(System.in);
		
		System.out.println("Enter Student Id: ");
		id = sc.nextLine();
		
		System.out.println("Enter Student Name: ");
		name = sc.nextLine();
		
		System.out.println("Is "+name+ "pass in exams(Yes/No)?: ");
		status = sc.nextLine();
		
		if(status.equals("Yes")) {
			passed = true;
		}
		
		if(status.equals("No")) {
			fail = true;
		}
		
		// close Scanner class object
		sc.close();
		
		// create Student object
		Student std = new Student(id, name, passed, fail);

		// create an instance of ObjectMapper class
	    	ObjectMapper mapper = new ObjectMapper();
	    
	    	// configure ObjectMapper globally
	    	mapper.configOverride(Boolean.class)
	    		.setFormat(JsonFormat.Value.forShape(Shape.NUMBER));
	    
	    	//serialize Student object to JSON
	    	String jsonString = mapper.writeValueAsString(std);
	    
	    	System.out.println("Java object after serializing:"+jsonString);
	}
	
}
class Student {

	private String stdId;
	private String stdName;
	private Boolean passed;
	private Boolean fail;

	public Student(String stdId, String stdName, Boolean passed, Boolean fail) {
		this.stdId = stdId;
		this.stdName = stdName;
		this.passed = passed;
		this.fail = fail;
	}
 
	public String getStdId() {
		return stdId;
	}
 
	public String getStdName() {
		return stdName;
	}
 
	public Boolean getPassed() {
		return passed;
	}
 
	public Boolean getFail() {
		return fail;
	}
 
}

输出

反序列化

与序列化一样，我们还需要对具有布尔变量的 0 和 1 值的字符串执行反序列化。因此，我们需要在将 JSON 字符串反序列化到我们的模型时从整数中获取布尔值。

不需要使用 **@JsonFormat** 注释或任何配置来将整数解析为布尔值，因为默认情况下 Jackson 会为我们执行此任务。

让我们看一个例子来了解如何完成反序列化

DeserializeIntegerIntoBooleanExample.java

//import  required classes and package if any
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
//create class DeserializeIntegerIntoBooleanExample to deserialize JSON string into pojo
public class DeserializeIntegerIntoBooleanExample {
	
	// main() method start
	public static void main(String args[]) throws JsonMappingException, JsonProcessingException{
		
		// JSON string to parse
		String jsonString = "{\"stdId\":\"121\", \"stdName\":\"Nicholas\", \"passed\":1, \"fail\":0}";

		// create an instance of ObjectMapper class
	    	ObjectMapper mapper = new ObjectMapper();
	    
	    	// deserialize JSON string into Java object
	    	Student std = mapper.readValue(jsonString, Student.class);
		
	    	// print student Id and Name
	    	System.out.println("Student Id: "+std.getStdId());
	    	System.out.println("Student Name: "+std.getStdName());
	    	System.out.println("is student passed?: "+std.getPassed());
	    	System.out.println("is student fail?: "+std.getFail());
	}
	
}

class Student {

	private String stdId;
	private String stdName;
	private Boolean passed;
	private Boolean fail;
	
	public Student() {
		this.stdId = null;
		this.stdName = null;
		this.passed = null;
		this.fail = null;
	}

	public Student(String stdId, String stdName, Boolean passed, Boolean fail) {
		this.stdId = stdId;
		this.stdName = stdName;
		this.passed = passed;
		this.fail = fail;
	}
 
	public String getStdId() {
		return stdId;
	}
 
	public String getStdName() {
		return stdName;
	}
 
	public Boolean getPassed() {
		return passed;
	}
 
	public Boolean getFail() {
		return fail;
	}
 
}

输出

数字字符串而不是整数

很多时候，我们需要将布尔值序列化/反序列化为数字字符串。让我们逐一了解序列化和反序列化

序列化为数字字符串

为了将布尔值序列化为数字字符串，我们需要创建一个自定义序列化器，然后使用它将布尔值序列化为数字字符串。

让我们首先创建一个自定义序列化器，即 NumericStringSerializer，然后我们将举一个例子，在该示例中使用此自定义序列化器将布尔值序列化为数字字符串。

NumericStringSerializer.java

// import required classes and package
import java.io.IOException;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;

// create custom serializer NumericStringSerializer by using JsonSerializer
public class NumericStringSerializer extends JsonSerializer<Boolean> {

	// override serialize() method of JsonSerializer
    	@Override
    	public void serialize(Boolean boolValue, JsonGenerator generator, SerializerProvider provider)
		throws IOException {
    	
    		// use writeString() method of JsonGenerator to parse boolean to numeric string
    		generator.writeString(boolValue ? "1" : "0");
    	}
}

SerializeBooleanToNumericString.java

//import required classes and package if any
import java.util.Scanner;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;

//create class SerializeBooleanToNumericString to serialize java object by mapping Boolean as a numeric string
public class SerializeBooleanToNumericString {
	
	// main() method start
	public static void main(String args[]) throws JsonProcessingException {
		
		String id, name, status;
		Boolean passed = false, fail = false;
		
		// create an instance of Scanner class
		Scanner sc = new Scanner(System.in);
		
		System.out.println("Enter Student Id: ");
		id = sc.nextLine();
		
		System.out.println("Enter Student Name: ");
		name = sc.nextLine();
		
		System.out.println("Is "+name+ "pass in exams(Yes/No)?: ");
		status = sc.nextLine();
		
		if(status.equals("Yes")) {
			passed = true;
		}
		
		if(status.equals("No")) {
			fail = true;
		}
		
		// close Scanner class object
		sc.close();
		
		// create Student object
		Student std = new Student(id, name, passed, fail);

		// create an instance of ObjectMapper class
	    	ObjectMapper mapper = new ObjectMapper();
	    
	    	//serialize Student object to JSON
	    	String jsonString = mapper.writeValueAsString(std);
	    
	    	System.out.println("Java object after serializing:"+jsonString);
	}
	
}
class Student {

	private String stdId;
	private String stdName;
 
	@JsonSerialize(using = NumericStringSerializer.class)
	private Boolean passed;
 
	@JsonSerialize(using = NumericStringSerializer.class)
	private Boolean fail;

	public Student(String stdId, String stdName, Boolean passed, Boolean fail) {
		this.stdId = stdId;
		this.stdName = stdName;
		this.passed = passed;
		this.fail = fail;
	}
 
	public String getStdId() {
		return stdId;
	}
 
	public String getStdName() {
		return stdName;
	}
 
	public Boolean getPassed() {
		return passed;
	}
 
	public Boolean getFail() {
		return fail;
	} 
}

输出

从数字字符串反序列化

与序列化一样，对于反序列化，我们还使用自定义反序列化器。我们将创建一个自定义反序列化器，然后我们将使用它将数字字符串反序列化为布尔值。

让我们首先创建一个自定义反序列化器，即 NumericStringDeserializer，然后我们将举一个例子，在该示例中使用此自定义反序列化器将数字字符串反序列化为布尔值。

NumericStringDeserializer.java

//import required classes and package
import java.io.IOException;
import com.fasterxml.jackson.core.JacksonException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;

//create custom deserializer NumericStringDeserializer by using JsonDeserializer
public class NumericStringDeserializer extends JsonDeserializer<Boolean> {

	// override deserialize() method of JsonDeserializer
	@Override
	public Boolean deserialize(JsonParser parser, DeserializationContext ctxt) throws IOException, JacksonException {
		
		// return true or false by comparing strings
		if(parser.getText().equals("0")) {
			return Boolean.FALSE;
		}
		if(parser.getText().equals("1")) {
			return Boolean.TRUE;
		}
		return null;
	}
	
}

DeserializeNumericStringToBoolean.java

//import  required classes and package if any
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;

//create class DeserializeNumericStringToBoolean to deserialize JSON string into pojo
public class DeserializeNumericStringToBoolean {
	
	// main() method start
	public static void main(String args[]) throws JsonMappingException, JsonProcessingException{
		
		// JSON string to parse
		String jsonString = "{\"stdId\":\"121\", \"stdName\":\"Nicholas\", \"passed\":\"1\", \"fail\":\"0\"}";

		// create an instance of ObjectMapper class
	    	ObjectMapper mapper = new ObjectMapper();
	    
	    	// deserialize JSON string into Java object
	    	Student std = mapper.readValue(jsonString, Student.class);
		
	    	// print student Id and Name
	    	System.out.println("Student Id: "+std.getStdId());
	    	System.out.println("Student Name: "+std.getStdName());
	    	System.out.println("is student passed?: "+std.getPassed());
	    	System.out.println("is student fail?: "+std.getFail());
	}
	
}

class Student {

	private String stdId;
	private String stdName;
	
	@JsonDeserialize(using = NumericStringDeserializer.class)
	private Boolean passed;
	
	@JsonDeserialize(using = NumericStringDeserializer.class)
	private Boolean fail;
	
	public Student() {
		this.stdId = null;
		this.stdName = null;
		this.passed = null;
		this.fail = null;
	}

	public Student(String stdId, String stdName, Boolean passed, Boolean fail) {
		this.stdId = stdId;
		this.stdName = stdName;
		this.passed = passed;
		this.fail = fail;
	}

	public String getStdId() {
		return stdId;
	}

	public String getStdName() {
		return stdName;
	}

	public Boolean getPassed() {
		return passed;
	}

	public Boolean getFail() {
		return fail;
	}

}

输出

下一个主题在 Jackson 中反序列化为集合/数组

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使用 Jackson 将布尔值序列化和反序列化为整数

序列化

字段级别配置

全局配置

反序列化

数字字符串而不是整数

序列化为数字字符串

从数字字符串反序列化

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使用 Jackson 将布尔值序列化和反序列化为整数

序列化

字段级别配置

全局配置

反序列化

数字字符串而不是整数

序列化为数字字符串

从数字字符串反序列化

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