Jackson反序列化/序列化不对属性进行排序 [英] Jackson deserialization/serialization does not sort properties

问题描述

我在应用程序中使用 Jackson 2.8.9 生成一些JSON。我有一些单元测试，在其中将生成的JSON与某些文件内容进行比较。

I'm using Jackson 2.8.9 in my application to generate some JSON. I have some unit tests in which I compare generated JSON with some files content.

当我将生成的JSON与文件内容进行比较时，由于属性的原因，它不匹配

When I compare my generated JSON with my file content, it does not match due to the properties order.

为了使测试可重复，我需要按字母顺序对属性进行排序。但是对于杰克逊，它似乎不起作用。

For the tests to be repeatable I need to have the properties sorted alphabetically. But with Jackson, it does not seems to work.

我写了一些关于幻觉的测试。只能通过 should_indent_properties 。

I wrote some tests for illustation. Only should_indent_properties pass.

public class FormatJsonWithJacksonTest {

private static final String INDENTED_UNSORTED = "{\r\n" + 
        "  \"firstChild\" : {\r\n" + 
        "    \"subChild\" : {\r\n" + 
        "      \"alphaItem\" : \"1234567891234567\",\r\n" + 
        "      \"otherProperty\" : \"2017-06-21\",\r\n" + 
        "      \"someOtherProperty\" : \"NONE\",\r\n" + 
        "      \"alphaType\" : \"KIND_OF_TYPE\"\r\n" + 
        "    }\r\n" + 
        "  }\r\n" + 
        "}";

private static final String INDENTED_SORTED = "{\r\n" + 
        "  \"firstChild\" : {\r\n" + 
        "    \"subChild\" : {\r\n" + 
        "      \"alphaItem\" : \"1234567891234567\",\r\n" + 
        "      \"alphaType\" : \"KIND_OF_TYPE\",\r\n" + 
        "      \"otherProperty\" : \"2017-06-21\",\r\n" + 
        "      \"someOtherProperty\" : \"NONE\"\r\n" + 
        "    }\r\n" + 
        "  }\r\n" + 
        "}";

private static final String UNINDENTED_UNSORTED = "{" + 
        "\"firstChild\":{" + 
        "\"subChild\":{" + 
        "\"alphaItem\":\"1234567891234567\"," + 
        "\"otherProperty\":\"2017-06-21\"," + 
        "\"someOtherProperty\":\"NONE\"," + 
        "\"alphaType\":\"KIND_OF_TYPE\"" + 
        "}" + 
        "}" + 
        "}";

private static final String UNINDENTED_SORTED = "{" + 
        "\"firstChild\":{" + 
        "\"subChild\":{" + 
        "\"alphaItem\":\"1234567891234567\"," + 
        "\"alphaType\":\"KIND_OF_TYPE\"," + 
        "\"otherProperty\":\"2017-06-21\"," + 
        "\"someOtherProperty\":\"NONE\"" + 
        "}" + 
        "}" + 
        "}";

@Test
public void should_sort_properties() throws Exception {
    // Given
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper = objectMapper
            .configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true);

    // When
    String formattedJson = tryingToFormatJson(objectMapper, INDENTED_UNSORTED);

    // Then
    assertEquals(UNINDENTED_SORTED, formattedJson);
}


@Test
public void should_indent_properties() throws Exception {
    // Given
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper = objectMapper.enable(SerializationFeature.INDENT_OUTPUT);

    // When
    String formattedJson = tryingToFormatJson(objectMapper, UNINDENTED_UNSORTED);

    // Then
    assertEquals(INDENTED_UNSORTED, formattedJson);
}

@Test
public void should_sort_and_indent_properties() throws Exception {
    // Given
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper = objectMapper
            .configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true)
            .enable(SerializationFeature.INDENT_OUTPUT);

    // When
    String formattedJson = tryingToFormatJson(objectMapper, INDENTED_UNSORTED);

    // Then
    assertEquals(INDENTED_SORTED, formattedJson);
}

//
// Utils
//

private String tryingToFormatJson(ObjectMapper objectMapper, String unformattedJson)
        throws IOException, JsonProcessingException {
    JsonNode unsortedTree = objectMapper.readTree(unformattedJson);
    Object treeToValue = objectMapper.treeToValue(unsortedTree, Object.class);
    return objectMapper.writeValueAsString(treeToValue);
}

}

• 我如何用Jackson排序JSON？


• 您有实现我的方法 tryingToFormatJson 的任何解决方案吗？


• 杰克逊（Jackson）是我执行此操作的正确工具吗？


• How could I sort my JSON with Jackson?
• Do you have any solution for implementing my method tryingToFormatJson?
• Is Jackson the right tool I want for doing this?

推荐答案

何时您调用 objectMapper.treeToValue（unsortedTree，Object.class）， Object 的类型是<$的子类c $ c>地图-只需放入 System.out.println（treeToValue.getClass（））进行检查。

When you call objectMapper.treeToValue(unsortedTree, Object.class), the Object's type is a subclass of Map - just put a System.out.println(treeToValue.getClass()) to check.

并根据 javadoc ， SORT_PROPERTIES_ALPHABETICALLY 不对映射键进行排序：

And according to javadoc, SORT_PROPERTIES_ALPHABETICALLY doesn't sort map keys:




功能，用于定义用于POJO字段的默认属性序列化顺序（注意：不适用于Map序列化离子！）





---





如果要对字段进行排序，您可以必须为您的结构创建自定义类，例如：

---

If you want to sort the fields, you have to create a custom class for you structure, like this:

public class Tree {
    private Map<String, Child> firstChild;

    // getters and setters
}

public class Child {
    private String alphaItem;

    private String otherProperty;

    private String someOtherProperty;

    private String alphaType;

    // getters and setters
}

然后更改 treeToValue 调用：

Tree treeToValue = objectMapper.treeToValue(unsortedTree, Tree.class);

通过此操作，字段将被排序并且测试将起作用。

With this, the fields will be sorted and the test will work.

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