The implementation principle of the HTML framework in the Java class library
Inquiry of the implementation principle of the HTML framework in the Java class library
introduction:
HTML is a tag language for creating web pages. In Java development, we usually need to process and generate HTML documents.In order to simplify development and improve efficiency, the Java class library covers many HTML frameworks. These frameworks provide powerful functions to process and generate HTML.This article will explore the principles of some common HTML frameworks in the Java library and demonstrate its usage through code examples.
1. FreeMarker framework
FreeMarker is a simple, flexible and powerful Java template engine, which is often used to generate dynamic HTML pages.Its implementation principle is mainly based on the combination of templates and data models.Let's take a look at an example first:
First of all, you need to introduce the dependencies of FreeMarker. You can manage it through Maven:
<dependency>
<groupId>org.freemarker</groupId>
<artifactId>freemarker</artifactId>
<version>2.3.31</version>
</dependency>
Then, create a Java class containing templates and data models:
import freemarker.template.Configuration;
import freemarker.template.Template;
import freemarker.template.TemplateException;
import java.io.IOException;
import java.io.StringWriter;
import java.util.HashMap;
import java.util.Map;
public class FreeMarkerExample {
public static void main(String[] args) throws IOException, TemplateException {
Configuration cfg = new Configuration(Configuration.VERSION_2_3_31);
cfg.setClassForTemplateLoading(FreeMarkerExample.class, "/");
cfg.setDefaultEncoding("UTF-8");
Template template = cfg.getTemplate("template.ftl");
Map<String, Object> dataModel = new HashMap<>();
dataModel.put("title", "FreeMarker Example");
dataModel.put("content", "This is a simple example of using FreeMarker.");
StringWriter writer = new StringWriter();
template.process(dataModel, writer);
System.out.println(writer.toString());
}
}
In the above example, we created a Java class containing templates and data models.Template.ftl can use the specific syntax of FreeMarker to generate the final HTML code by inserting the value of the data model in the template file.Then, we handle the template by calling the `Template.process (DataModel, Writer) method to fill the value in the data model into the template.Finally, we use the method of `writer.tostring ()` to obtain the final HTML code.
2. Thymeleaf framework
Thymeleaf is a server -side Java template engine that is used to create a dynamic HTML page.Its implementation principle is to generate the final HTML code by parsing the template file and replacing the attribute values in it.The following is an example:
First of all, you need to introduce the dependencies of Thymeleaf. You can manage it through Maven:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
Then, create a Java class containing templates and data models:
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.ModelAndView;
@RestController
public class ThymeleafExample {
@GetMapping("/example")
public ModelAndView example(Model model) {
model.addAttribute("title", "Thymeleaf Example");
model.addAttribute("content", "This is a simple example of using Thymeleaf.");
return new ModelAndView("template");
}
}
In the above example, we created a Java class containing templates and data models, and used the `@RESTController` annotation marker as a controller.In the `Example` method, we pass the value in the data model into the template view through the` Model` object.Finally, we return an object containing a template name, which is used to render the final HTML page.
3. JSOUP library
JSOUP is a Java -based HTML parser used to extract and operate data from HTML documents.Its implementation principle is to analyze the HTML document to build a data structure similar to the DOM tree, and then obtain, modify and operate node data by provided APIs.The following is an example:
First of all, you need to introduce the dependencies of JSOUP. You can manage it through Maven:
<dependency>
<groupId>org.jsoup</groupId>
<artifactId>jsoup</artifactId>
<version>1.13.1</version>
</dependency>
Then, use JSOUP to parse the HTML document and extract the data:
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.select.Elements;
import java.io.IOException;
public class JsoupExample {
public static void main(String[] args) throws IOException {
String html = "<html><body><div id='content'>Hello, Jsoup!</div></body></html>";
Document doc = Jsoup.parse(html);
Elements content = doc.select("#content");
System.out.println(content.text());
}
}
In the above example, we use the JSOUP's `PARSE` method to resolve the HTML document and obtain data from a specific node through the CSS selector.In this example, we can obtain an element with the ID to `Content` by the`#Content "selector, and use the` Text () "method to obtain its text content.
in conclusion:
The HTML framework implementation principles in the Java class library are different, but they all provide simple, flexible and powerful functions to process and generate HTML documents.By using these frameworks, we can more easily operate HTML and easily create dynamic and interactive web applications.
Remark:
The above examples are only simplified instructions, and more complicated code and configuration may be needed in actual use.Complete example code and more details can be found in related documents and official websites.
