如何使用Java和Jackson附加到JSON [英] How to append to JSON with Java and Jackson

问题描述

我正在尝试一个简单的测试，其中的代码会添加一些json条目，但是每次都会被覆盖(json文件在运行后将仅包含1个条目).我知道我需要使用'[]'在JSON中创建一个数组，但是我该怎么做呢?另外，还有更好的方法吗?我一直在搜索，每个库似乎都笨拙，上面有许多用户编写的代码.谢谢

I'm trying a simple test where the code appends a few json entries, however it is getting overwritten each time (the json file will only have 1 entry in it after running). I know I need to somehow create an array in JSON using '[]', but how would I go about doing that? Also, is there a better way to be doing this? I've been searching around and every library seems clunky with lots of user written code. Thanks

public class REEEE {

private static Staff createStaff() {

    Staff staff = new Staff();

    staff.setName("mkyong");
    staff.setAge(38);
    staff.setPosition(new String[] { "Founder", "CTO", "Writer" });
    Map<String, Double> salary = new HashMap() {
        {
            put("2010", 10000.69);
        }
    };
    staff.setSalary(salary);
    staff.setSkills(Arrays.asList("java", "python", "node", "kotlin"));

    return staff;
}

public static void main(String[] args) throws IOException {
    ObjectMapper mapper = new ObjectMapper();

    File file = new File("src//j.json");        
    for(int i = 0; i < 4; i++) {
        Staff staff = createStaff();

        try {
            // Java objects to JSON file
            mapper.writeValue(file, staff);

            // Java objects to JSON string - compact-print
            String jsonString = mapper.writeValueAsString(staff);

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

推荐答案

您可以在List中添加人员，然后将列表写入文件，如下所示，

You can add staff in List and then write the list to file as below,

List<Staff> staffList = new LinkedList<>()
for(int i = 0; i < 4; i++) {
    Staff staff = createStaff();
    staffList.add(staff);
}
mapper.writeValue(file, staffList);

希望有帮助.

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