Jackson序列化csv属性顺序

Question

我们有一张350列的桌子。pojo类被生成，getter命令被打乱。试图使用jackson提供的csvmapper，但它会根据getter顺序生成csv@JsonPropertyOrder也不适合使用，因为有很多列。我们用xml维护列顺序，并且可以在运行时生成字段顺序数组。我们可以在运行时重写以提供属性排序的字段名数组吗？我们可以使用注释内省器进行自定义吗？

Answer 1

我相信您在这里唯一的选择是uniVocity解析器，因为它允许您选择要编写的列以及顺序：

CsvWriterSettings settings = new CsvWriterSettings();
// Sets the file headers (used for selection only, these values won't be written automatically)
settings.setHeaders("Year", "Make", "Model", "Description", "Price");

// Selects which fields from the input should be written. In this case, fields "make" and "model" will be empty
// The field selection is not case sensitive
settings.selectFields("description", "price", "year");

//configures the writer process java beans with annotations (assume TestBean has a few annotated fiedls)
settings.setRowWriterProcessor(new BeanWriterProcessor<TestBean>(TestBean.class));

// Creates a writer with the above settings;
CsvWriter writer = new CsvWriter(new File("/path/to/output.csv"), settings);

// Writes the headers specified in the settings
writer.writeHeaders();

//creates a bean instance for writing
TestBean bean = new TestBean();
bean.setPrice(new BigDecimal("500.33"));
bean.setDescription("Blah,blah");
bean.setYear(1997);

//writes it
writer.processRecord(bean);

writer.close();

希望有帮助。

披露：我是这个库的作者，它是开源和免费的（Apache 2.0 License）

Answer 2

以防你在2020年到达这里，这直接来自留档。

那么，如何使用CSV模式实例呢？有三种方法：

• 基于Java类创建模式

// Schema from POJO (usually has @JsonPropertyOrder annotation)
CsvSchema schema = mapper.schemaFor(Pojo.class);

// Manually-built schema: one with type, others default to "STRING"
CsvSchema schema = CsvSchema.builder()
        .addColumn("firstName")
        .addColumn("lastName")
        .addColumn("age", CsvSchema.ColumnType.NUMBER)
        .build();

// Read schema from the first line; start with bootstrap instance
// to enable reading of schema from the first line
// NOTE: reads schema and uses it for binding
CsvSchema bootstrapSchema = CsvSchema.emptySchema().withHeader();
ObjectMapper mapper = new CsvMapper();
mapper.readerFor(Pojo.class).with(bootstrapSchema).readValue(json);

Answer 3

你要找的是MappingFeature。您需要禁用属性的字母数字排序，这在默认情况下是启用的：

CsvMapper mapper = new CsvMapper();
mapper.disable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);

有关此的更多信息，您可以在此处找到：在CsvSchema中添加一个功能以允许定义排序#42