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How to use Jackson for Java serialization?

王林
王林Original
2024-04-16 17:03:011181browse

使用Jackson进行Java序列化可以分为以下步骤:添加Jackson依赖项:com.fasterxml.jackson.core:jackson-databind。创建POJO对象:定义一个包含与JSON结构对应的getter和setter方法的Java对象。创建ObjectMapper对象:实例化ObjectMapper,负责序列化和反序列化。序列化对象:使用ObjectMapper将对象序列化为JSON。实战示例:使用JDBC查询数据库并将其结果序列化为JSON。反序列化对象:使用ObjectMapper从JSON字符串反序列化对象。

How to use Jackson for Java serialization?

如何使用Jackson进行Java序列化

简介

Jackson是一个用于Java对象的JSON序列化和反序列化的流行库。本文将指导您如何使用Jackson在Java应用程序中进行序列化。

添加Jackson依赖项

在您的Maven或Gradle项目中添加以下依赖项:

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.13.4</version>
</dependency>

创建POJO对象

定义要序列化的POJO(普通旧Java对象)类,该类包含与JSON结构对应的getter和setter方法。例如:

public class User {
    private String name;
    private int age;
    // 省略getter和setter方法
}

创建ObjectMapper对象

Jackson的关键组件是ObjectMapper,它负责序列化和反序列化。创建ObjectMapper实例:

ObjectMapper mapper = new ObjectMapper();

序列化对象

使用ObjectMapper将对象序列化为JSON:

User user = new User();
user.setName("John Doe");
user.setAge(30);

String json = mapper.writeValueAsString(user);
System.out.println(json); // 输出:{"name":"John Doe","age":30}

实战示例

假设您有存储用户数据的数据库表。您可以编写以下代码来查询用户并将其序列化为JSON:

try (Connection conn = DriverManager.getConnection(DB_URL, USER, PASSWORD)) {
    Statement stmt = conn.createStatement();
    String sql = "SELECT * FROM users";
    ResultSet rs = stmt.executeQuery(sql);

    List<User> users = new ArrayList<>();
    while (rs.next()) {
        User user = new User();
        user.setId(rs.getInt("id"));
        user.setName(rs.getString("name"));
        user.setAge(rs.getInt("age"));
        users.add(user);
    }

    String json = mapper.writeValueAsString(users);
    System.out.println(json); // 输出:[{},{},...]
} catch (SQLException | IOException e) {
    e.printStackTrace();
}

反序列化对象

使用ObjectMapper从JSON字符串反序列化对象:

User user = mapper.readValue(json, User.class);
System.out.println(user.getName()); // 输出:John Doe

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