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Converting JSON to Map<String, String> in Java

Use case: You receive a JSON string like {"Key":"value"} (perhaps from an API or file), and you want to convert it into a Java Map<String, String> for easier manipulation.

✅ Using Jackson

1. Add Jackson Dependency (if using Maven)

xml

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.16.0</version> <!-- Use latest version -->
</dependency>

2. Sample Code

java

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.util.Map;

public class JacksonJsonToMap {
    public static void main(String[] args) throws Exception {
        String json = "{\"Key\":\"value\"}";

        ObjectMapper objectMapper = new ObjectMapper();
        Map<String, String> map = objectMapper.readValue(json, new TypeReference<Map<String, String>>() {});

        System.out.println(map); // Output: {Key=value}
    }
}

🔍 Explanation:

• ObjectMapper is the main class in Jackson for JSON parsing.
• TypeReference<Map<String, String>>() {} is used to ensure proper typing and avoid raw type warnings.

✅ Using Gson

1. Add Gson Dependency (if using Maven)

xml

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.10.1</version> <!-- Use latest version -->
</dependency>

2. Sample Code

java

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

import java.lang.reflect.Type;
import java.util.Map;

public class GsonJsonToMap {
    public static void main(String[] args) {
        String json = "{\"Key\":\"value\"}";

        Gson gson = new Gson();
        Type type = new TypeToken<Map<String, String>>(){}.getType();
        Map<String, String> map = gson.fromJson(json, type);

        System.out.println(map); // Output: {Key=value}
    }
}

🔍 Explanation:

• Gson provides a simple way to deserialize a JSON string.
• TypeToken<Map<String, String>>(){}.getType() ensures proper type handling at runtime.

⚖️ Comparison: Jackson vs Gson

FeatureJacksonGsonPerformanceFaster for large or complex JSONSlightly slowerConfigurationHighly customizableSimpler, less configuration neededTypingStrong typing via TypeReferenceUses TypeToken for genericsPopularityWidely used in enterprise applicationsCommon in Android and lightweight apps

✅ Output (Both Methods)

plaintext

{Key=value}

✅ Use in Spring Boot

In Spring Boot apps, Jackson is included by default, so if you're using Spring, you likely don’t need to add extra dependencies—just inject and use ObjectMapper.