How to use FreeMarker template to complete page static processing in SpringBoot2

1. Page staticization

1. Dynamic and static pages

Static page

is a static web page, which refers to a loaded HTML page. , without the need to go through the request server data and compilation process, it is directly loaded to the client's browser and displayed. In layman's terms, it means generating an independent HTML page without data interaction with the server.

Description of advantages and disadvantages:

• The content of static web pages is stable and the page loading speed is extremely fast;

• Does not interact with the server , to improve security;

• The interactivity of static web pages is poor, and the real-time data is very low;

• The dimensionality cost is high and many HTML pages are generated;

Dynamic page

refers to a web programming technology that is opposite to static web pages. The content of the page needs to be obtained by requesting the server, without considering caching. When the data in the service interface changes, the content loaded on the page will also change in real time, but the displayed content will dynamically change with the results of the database operation.

Description of advantages and disadvantages:

• Real-time acquisition of data from dynamic web pages, low latency;

• Depends on database interaction, page The maintenance cost is very low;

• Real-time interaction with the database, the cost of security control is high;

• The page loading speed is very dependent on the performance of the database and service ;

Dynamic pages and static pages have a strong correlation, and they are easier to understand by comparison.

2. Application scenarios

There are many application scenarios for static processing of dynamic pages, such as:

• The header and bottom of large websites, static Unified loading after transformation;

• Media websites, the content is rendered and directly converted into HTML web pages;

• Under high concurrency, CDN edge node proxy Static web pages;

• In e-commerce websites, complex product details page processing;

The foundation of static technology: prompt service response Speed, or to advance the response node, such as general processes, page (client) request service, service processing, response data, page loading, a series of processes are not only complex, but also time-consuming, if processed based on static technology , load the static page directly, and the request ends.

2. Process Analysis

Static page conversion is a relatively complex process, and the core process is as follows:

• Develop a page template, that is, a static web page style;

• Provide an interface to obtain data for the page template;

• Write data in the page template The parsing process of interface return parameters;

• Based on the parsing engine, merge the data with the page template;

• After the page template content is loaded, it is converted to HTML static page;

• HTML static page is uploaded to the file server;

• The client (Client) obtains the url loading display of the static page;

The main process is roughly as above. If the data interface response parameters change, the static page needs to be regenerated, so the real-time performance of data loading will be much lower.

3. Code implementation case

1. Basic dependencies

FreeMarker is a template engine: a template based on the data to be changed, and used to generate output text (HTML web pages, emails, configuration files, source code, etc.)

<dependency>
    <groupid>org.springframework.boot</groupid>
    <artifactid>spring-boot-starter-freemarker</artifactid>
</dependency>

2. Page template

The template style developed by FreeMarker is used here.

    <title>PageStatic</title>


主题：${myTitle}<br>


作者：${data.auth} 日期：${data.date}<br>

规格描述	产品详情
${info.desc}

The syntax of FreeMarker is basically the same as the original HTML syntax, but it has its own set of data processing tags, which is not complicated to use.

3. Parsing process

Through parsing, the data of the page template and data interface can be merged together.

@Service
public class PageServiceImpl implements PageService {
    private static final Logger LOGGER = LoggerFactory.getLogger(PageServiceImpl.class) ;
    private static final String PATH = "/templates/" ;
    @Override
    public void ftlToHtml() throws Exception {
        // 创建配置类
        Configuration configuration = new Configuration(Configuration.getVersion());
        // 设置模板路径
        String classpath = this.getClass().getResource("/").getPath();
        configuration.setDirectoryForTemplateLoading(new File(classpath + PATH));
        // 加载模板
        Template template = configuration.getTemplate("my-page.ftl");
        // 数据模型
        Map<string> map = new HashMap();
        map.put("myTitle", "页面静态化(PageStatic)");
        map.put("tableList",getList()) ;
        map.put("imgList",getImgList()) ;
        // 静态化页面内容
        String content = FreeMarkerTemplateUtils.processTemplateIntoString(template, map);
        LOGGER.info("content:{}",content);
        InputStream inputStream = IOUtils.toInputStream(content,"UTF-8");
        // 输出文件
        FileOutputStream fileOutputStream = new FileOutputStream(new File("F:/page/newPage.html"));
        IOUtils.copy(inputStream, fileOutputStream);
        // 关闭流
        inputStream.close();
        fileOutputStream.close();
    }
    private List<tableinfo> getList (){
        List<tableinfo> tableInfoList = new ArrayList() ;
        tableInfoList.add(new TableInfo(Constant.desc1, Constant.img01));
        tableInfoList.add(new TableInfo(Constant.desc2,Constant.img02));
        return tableInfoList ;
    }
    private List<string> getImgList (){
        List<string> imgList = new ArrayList() ;
        imgList.add(Constant.img02) ;
        imgList.add(Constant.img02) ;
        return imgList ;
    }
}</string></string></tableinfo></tableinfo></string>

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