Jackson(ObjectMapper)的簡單使用(可轉xml)

參考文章：http://www.cnblogs.com/hoojo/archive/2011/04/22/2024628.html  (原文章更詳細哦,且有介紹xml與java對象的互轉)

參考文章作者：hoojo

本例maven配置：

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.4.1</version>
        </dependency>
        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-jaxrs</artifactId>
            <version>1.9.11</version>
        </dependency>

測試代碼：

import java.io.IOException;

import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.ObjectMapper;

public class TestJackSon {

    // 聲明兩個轉換器
    private ObjectMapper objectMapper = null; // 一般使用ObjectMapper就已足夠
    private JsonGenerator jsonGenerator = null; // 需要關閉

    /**
     * Java對象轉換成JSON_1（objectMapper）
     */
    public void test1() {
        // 實例化轉換器
        objectMapper = new ObjectMapper();

        // 測試
        try {
            User user = new User("ZhangSan", 25, "[e-mail]");

            // 直接輸出轉化結果到服務台，返回void
            System.out.println("直接輸出到服務台：");
            objectMapper.writeValue(System.out, user); // user可替換為List,Map等等其他類型,都可正常輸出

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * Java對象轉換成JSON_2（objectMapper）
     */
    public void test2() {
        // 實例化轉換器
        objectMapper = new ObjectMapper();

        // 測試
        try {
            User user = new User("ZhangSan", 25, "[e-mail]");
            // 返回String
            String json = objectMapper.writeValueAsString(user); // user可替換為List,Map等等其他類型,都可正常輸出
            System.out.println("返回String：");
            System.out.println(json);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * Json轉Java對象（objectMapper）
     */
    public void test3() {
        // 實例化轉換器
        objectMapper = new ObjectMapper();

        // 測試
        try {
            String json = "{\"name\":\"ZhangSan\",\"age\":25,\"emailAddress\":\"[e-mail]\"}";
            User user = objectMapper.readValue(json, User.class);

            System.out.println(user.getName() + " | " + user.getAge() + " | " + user.getEmailAddress());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * jsonGenerator的簡單使用
     */
    public void test4() {
        // 實例化轉換器
        objectMapper = new ObjectMapper();
        try {
            jsonGenerator = objectMapper.getJsonFactory().createJsonGenerator(System.out, JsonEncoding.UTF8);
            User user = new User("ZhangSan", 25, "[e-mail]");

            // 測試
            System.out.println("jsonGenerator:");
            jsonGenerator.writeObject(user); //直接輸出到控制台

            // jsonGenerator需要關閉
            if (jsonGenerator != null) {
                jsonGenerator.flush();
            }
            if (!jsonGenerator.isClosed()) {
                jsonGenerator.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 測試main
     */
    public static void main(String[] args) {
        TestJackSon test = new TestJackSon();
        test.test4();
    }

}

class User {

    public String name;

    public int age;

    public String emailAddress;

    /**
     * 構造函數
     */
    public User(String name, int age, String emailAddress) {
        super();
        this.name = name;
        this.age = age;
        this.emailAddress = emailAddress;
    }

    // getters/setters(略)

}

 

追加記錄(2017-02-16)：

可增加如下配置，解決json中屬性多於java對象中屬性時報錯的問題.

objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
XXX xxx = objectMapper.readValue(jsonResult, XXX.class);