Jackson DataFormats: technical principles analysis of technical principles in the Java library

Jackson is an open source Java library that provides an efficient way to handle the mutual conversion between Java objects and JSON.It mainly contains two core modules: the core of Jackson and Jackson DataFormats. Jackson's core module is the core part of the Jackson library, which provides the basic function of JSON processing.It uses a highly optimized algorithm that can quickly analyze JSON and convert it to Java objects, and can also convert the Java object into JSON.Jackson's core module mainly includes the following key categories: 1. ObjectMapper: This is the main engine class of Jackson to perform conversion operations between Java objects and JSON.It provides a series of methods, such as Readvalue () to convert JSON to Java objects, Writevalueasstring () is used to convert Java objects into JSON string. 2. JSONPARSER and JSONGENERATOR: These two categories are used to analyze and generate JSON text.JSONPARSER is responsible for parsing JSON text into JSON nodes, while JSONGENRATOR is responsible for generating the corresponding JSON text to generate the JSON node. 3. JSONNODE: This class represents a JSON node, which can represent a JSON object, a JSON array or a JSON property.Using JSONNODE can easily read and modify JSON. The Jackson DataFormats module is the extension of the Jackson library, which provides support for different data formats.Among them, the Text framework is one of them.The Text framework provides a method of using text format for data storage and transmission, such as CSV, Properties files. To use the Text framework, we need to add corresponding dependencies.Take Maven as an example, you can add the following dependencies to the pom.xml file: <dependency> <groupId>com.fasterxml.jackson.dataformat</groupId> <artifactId>jackson-dataformat-csv</artifactId> <version>${jackson.version}</version> </dependency> Next, we can use the Text framework for the read and write operation of the CSV file.The following is a simple example code: public class CsvExample { public static void main(String[] args) throws IOException { CsvMapper csvMapper = new CsvMapper(); File csvFile = new File("data.csv"); // Read data from the CSV file MappingIterator<Map<String, String>> iterator = csvMapper.readerFor(Map.class) .with(CsvSchema.emptySchema().withHeader()) .readValues(csvFile); // Traversing data while (iterator.hasNext()) { Map<String, String> row = iterator.next(); System.out.println(row); } // Write data to the CSV file ObjectWriter writer = csvMapper.writerFor(Map.class) .with(CsvSchema.emptySchema().withHeader()); writer.write(new FileOutputStream("output.csv"), Collections.singletonMap("name", "John Doe")); } } The above code first creates a CSVMapper object, and then specifies the data type to be read through the readerfor () method, and then calls the Readvalues () method to read the data from the CSV file.Then, by traversing the MappingIterator, we can obtain the data we read one by one.Finally, the data type to be written was specified using the WRITERFOR () method, and the data is written into the CSV file through the WRITE () method. In general, the Text framework of Jackson provides a convenient way to process the data format data for Java developers, which can improve the storage and transmission efficiency of data.By using the Jackson library, we can easily implement mutual conversion operations between Java objects and text formats.