Java json字符串 转 mapper 再取出键值对

在 Java 中，可以使用 Jackson 库将 JSON 字符串转换为 Java 对象（mapper），然后再从 mapper 中取出键值对。具体操作步骤如下：

1. 引入 Jackson 库

<!-- pom.xml 文件中 -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.12.3</version>
</dependency>

2. 将 JSON 字符串转换为 mapper

import com.fasterxml.jackson.databind.ObjectMapper;

String jsonString = "{\"name\":\"Tom\",\"age\":20}";
ObjectMapper mapper = new ObjectMapper();
Map<String, Object> map = mapper.readValue(jsonString, Map.class);

3. 从 mapper 中取出键值对

String name = (String) map.get("name");
int age = (int) map.get("age");
System.out.println("姓名：" + name);
System.out.println("年龄：" + age);

完整代码如下：

import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.Map;

public class JsonMapperDemo {
    public static void main(String[] args) throws Exception {
        String jsonString = "{\"name\":\"Tom\",\"age\":20}";
        ObjectMapper mapper = new ObjectMapper();
        Map<String, Object> map = mapper.readValue(jsonString, Map.class);
        String name = (String) map.get("name");
        int age = (int) map.get("age");
        System.out.println("姓名：" + name);
        System.out.println("年龄：" + age);
    }
}