Template engine and Freemarker

The goal of the template engine is "data + template = result"

Template engine effectively "decouples" data from presentation

template engine

Mainstream template engine

Java Server Page(JSP)
Freemarker
Beetle

Freemarker

Freemarker is a free and open source template engine technology

Freemarker script is Freemarker Template Language

Freemarker provides a number of built-in functions to simplify development

JSP and Freemarker

	JSP	Freemarker
Official standard	yes	no
Execution mode	Compiled type	Interpretive type
Execution efficiency	high	low
Development efficiency	low	high
Expansion capability	weak	strong
Data extraction	JSTL+EL	Built in label

Freemarker quick start

Freemaker Chinese online manual: http://freemarker.foofun.cn/

Create a new ordinary java project, create a new lib folder, and import the jar package freemaker Jar and create a freemarker sample1. Jar under the freemaker package Java class and sample1 ftl file, double-click sample1 ftl file Eclipse will pop up a prompt to install the editing plug-in of ftl file. After installing the plug-in, only the file code will be highlighted. If it is not installed, it will not affect the development. Create a Computer class under the entity package as a subsequent test data class.

FTL value

The value of ${attribute name} can be used to calculate the attribute

${property name! Default value} if the property does not exist, use the default value

${attribute name? string} formatted output

Branch judgment

if branch judgment

switch branch judgment

freemarker.FreemarkerSample1.java

package freemarker;

import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import entity.Computer;
import freemarker.core.ParseException;
import freemarker.template.Configuration;
import freemarker.template.MalformedTemplateNameException;
import freemarker.template.Template;
import freemarker.template.TemplateException;
import freemarker.template.TemplateNotFoundException;

public class FreemarkerSample1 {

	public static void main(String[] args) throws TemplateNotFoundException, MalformedTemplateNameException, ParseException, IOException, TemplateException {
		//1. Load template 	 Note that the passed in construction parameter specifies the version number of freemaker. Different versions of freemaker have different parsing syntax
		//Create core configuration object
		Configuration config = new Configuration(Configuration.VERSION_2_3_31);
		//Set load directory 	 In freemarkersample1 Class class loads the specified ftl file, and the second parameter empty string represents the current package
		config.setClassForTemplateLoading(FreemarkerSample1.class, "");
		//Get template object
		Template t = config.getTemplate("sample1.ftl");
		
		//2. Create data
		Map<String,Object> data = new HashMap<String,Object>();
		data.put("site", "Baidu");
		data.put("url", "http://www.baidu.com");
		data.put("date", new Date());
		data.put("number", 2165464.565465);
		//You can also use complex data types
		Map info = new HashMap();
		info.put("cpu", "i5");
		Computer c1 = new Computer("1234567","ThinkPad",2,null,new Date(),12900f,info);
		data.put("computer",c1);
		//3. Generate output system Out is the output byte stream, while process needs to pass in the character stream. Use OutputStreamWriter to convert the byte stream into the character stream
		t.process(data, new OutputStreamWriter(System.out));
	}
}

sample1.ftl

<#--Freemarker value -- >
${site}
${url}
<#--Default value -- >
${author!"Nonexistent property"}
<#--Formatted output -- >
${date?string("yyyy year MM month dd day HH:mm:ss SSS")}
${number?string("0.00")}
<#--In Freemarker, you only need "= =" to judge the equality of strings, instead of using equals -- > in java
<#if computer.sn=="1234567">
Important equipment
</#if>
SN:${computer.sn}
model:${computer.model}
<#if computer.state==1>
state:In use
<#elseif computer.state==2>
state:let ... lie idle 
<#elseif computer.state==2>
state:Scrap
</#if>

<#switch computer.state>
	<#Case 1 > status: in use
		<#break>
	<#Case 2 > status: idle
		<#break>
	<#Case 3 > status: Scrap
		<#break>
	<#Default > status: invalid status
</#switch>

<#-- ?? Indicates whether the object is null and returns true / false -- >
<#if computer.user??>
user:${computer.user}
</#if>
Procurement time:${computer.dop?string("yyyy year MM month dd day")}
Purchase price:${computer.price?string("0.00")}
-----------------------
CPU:${computer.info["cpu"]}
Memory:${computer.info["memory"]!"No memory information"}

entity.Computer.java

package entity;

import java.util.Date;
import java.util.Map;

public class Computer {
	private String sn; //serial number
	private String model;
	private int state;	//Status 1 - in use 2 - idle 3 - scrapped
	private String user;	//User
	private Date dop;	//Purchase date
	private Float price;
	private Map info;	//Computer configuration information
	
	public Computer() {}
	
	public Computer(String sn, String model, int state, String user, Date dop, Float price, Map info) {
		super();
		this.sn = sn;
		this.model = model;
		this.state = state;
		this.user = user;
		this.dop = dop;
		this.price = price;
		this.info = info;
    }
	public String getSn() {return sn;}
	public void setSn(String sn) {this.sn = sn;}
	public String getModel() {return model;}
	public void setModel(String model) {this.model = model;}
	public int getState() {return state;}
	public void setState(int state) {this.state = state;}
	public String getUser() {return user;}
	public void setUser(String user) {this.user = user;}
	public Date getDop() {return dop;}
	public void setDop(Date dop) {this.dop = dop;}
	public Float getPrice() {return price;}
	public void setPrice(Float price) {this.price = price;}
	public Map getInfo() {return info;}
	public void setInfo(Map info) {this.info = info;}
}

List, iteration list, Map

Iterative variable + underlined index can obtain the index value of the current cycle

list iteration Map

Freemarkersample1 Data replacement in step 2 of Java

//2. Create data
//Test data of iterative list
Map<String,Object> data = new HashMap<String,Object>();
List<Computer> computers = new ArrayList();
computers.add(new Computer("1234567","ThinkPad",2,null,new Date(),12900f,new HashMap()));
computers.add(new Computer("1234565","HP",2,"Hundred and six",new Date(),12900f,new HashMap()));
computers.add(new Computer("1234568","DELL",2,"Small A",new Date(),12900f,new HashMap()));
data.put("computers", computers);
//Test data of iterative Map
//HashMap is out of order, and LinkedHashMap can ensure that the data is stored in order for extraction
Map computerMap = new LinkedHashMap();
for(Computer c:computers) {
    computerMap.put(c.getSn(), c);
}
data.put("computer_map", computerMap);

sample1.ftl

<#list computers as computer>
Serial number:${computer_index+1}	<#--Iterative variable_ Index saves the index of the loop -- >
SN:${computer.sn}
model:${computer.model}
<#switch computer.state>
<#case 1>
state:In use
<#break>
<#case 2>
state:let ... lie idle
<#break>
<#case 3>
state:Scrap
<#break>
<#default>
state:invalid state
</#switch>
<#if computer.user??>
user:${computer.user}
</#if>
Procurement time:${computer.dop?string("yyyy year MM month dd day")}
Purchase price:${computer.price?string("0.00")}
CPU:${computer.info["cpu"]!"nothing CPU information"}
Memory:${computer.info["memory"]!"No memory information"}
-----------------------
</#list>
=================================
<#list computer_map?keys as k>
${k}-${computer_map[k].model}
${computer_map[k].price?string("0.00")}
<#--Others are not written by analogy -- >
-----------------------
</#list>

Built in function (common)

Freemaker Chinese online manual: http://freemarker.foofun.cn/

Freemarkersample1 Data replacement in step 2 of Java

//2. Create data
Map<String,Object> data = new HashMap<String,Object>();
data.put("name", "jackson");
data.put("brand", "bmw");
data.put("words", "first blood");
data.put("n", 34324.3432);
data.put("date", new Date());
List<Computer> computers = new ArrayList();
computers.add(new Computer("1234567","ThinkPad",2,null,new Date(),12900f,new HashMap()));
computers.add(new Computer("1234565","HP",2,"Hundred and six",new Date(),14900f,new HashMap()));
computers.add(new Computer("1234568","DELL",2,"Small A",new Date(),12000f,new HashMap()));
data.put("computers", computers);

sample1.ftl

${name?cap_first}
${brand?upper_case}
${brand?length}
${words?replace("blood","*****")}
${words?index_of("blood")}
<#--Use? string implements the operation of ternary operator -- >
${(words?index_of("blood")!=-1)?string("Contains sensitive words","Does not contain sensitive words")}

${n?round}
${n?floor}
${n?ceiling}

Co owned by the company ${computers?size}Computers
 First set:${computers?first.model}
Last one:${computers?last.model} 

<#--Collection sorting function sort_by(), plus reverse, the reverse sort is the descending sort -- >
<#list computers?sort_by("price")?reverse as c>
	${c.sn}-${c.price}
</#list>

Freemarker and Servlet integration

The project structure is as follows:

Import freemaker.exe from the WEB-INF/lib folder Jar package

Create a new employee in the ftl folder ftl, copy the prepared html code, and store static resources such as CSS, fonts and JS at the same level as WEB-INF

web.xml configuration freemaker

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>fm-web</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <!-- servlet And freemarker Integration is by FreemarkerServlet Class implemented -->

  <servlet>
  	<servlet-name>freemarker</servlet-name>
  	<servlet-class>freemarker.ext.servlet.FreemarkerServlet</servlet-class>
  	<!-- Script file storage directory, access to.ftl End file mapped to/WEB-INF/ftl -->
  	<init-param>
  		<param-name>TemplatePath</param-name>
  		<param-value>/WEB-INF/ftl</param-value>
  	</init-param>
  </servlet>
  <servlet-mapping>
  	<servlet-name>freemarker</servlet-name>
  	<url-pattern>*.ftl</url-pattern>
  </servlet-mapping>
</web-app>

Employee.java employee data template class

package freemarker.servlet;

public class Employee {
	private Integer empno;
	private String ename;
	private String department;
	private String job;
	private Float salary;
	
	public Employee() {}
	public Employee(Integer empno, String ename, String department, String job, Float salary) {
		super();
		this.empno = empno;
		this.ename = ename;
		this.department = department;
		this.job = job;
		this.salary = salary;
	}
	
	public Integer getEmpno() {
		return empno;
	}
	public void setEmpno(Integer empno) {
		this.empno = empno;
	}
	public String getEname() {
		return ename;
	}
	public void setEname(String ename) {
		this.ename = ename;
	}
	public String getDepartment() {
		return department;
	}
	public void setDepartment(String department) {
		this.department = department;
	}
	public String getJob() {
		return job;
	}
	public void setJob(String job) {
		this.job = job;
	}
	public Float getSalary() {
		return salary;
	}
	public void setSalary(Float salary) {
		this.salary = salary;
	}
}

ListServlet.java background provides data

package freemarker.servlet;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class ListServlet
 */
@WebServlet("/list")
public class ListServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ListServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		List list = new ArrayList();
		list.add(new Employee(7332,"Xiao Wang","Marketing Department","Customer representative",5654f));
		list.add(new Employee(8832,"Small B","R & D department","Operation and maintenance engineer",7000f));
		request.setAttribute("employee_list", list);
//		Request forwarding jump
		request.getRequestDispatcher("/employee.ftl").forward(request,response);
	}
}

employee.ftl list iteration list display data

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <title>Employee list</title>
    <link href="css/bootstrap.css" type="text/css" rel="stylesheet"></link>
    
    <script type="text/javascript" src="js/jquery-1.11.1.min.js"></script>
    <script type="text/javascript" src="js/bootstrap.js"></script>
 
    <style type="text/css">
        .pagination {
            margin: 0px
        }
 
        .pagination > li > a, .pagination > li > span {
            margin: 0 5px;
            border: 1px solid #dddddd;
        }
 
        .glyphicon {
            margin-right: 3px;
        }
 
        .form-control[readonly] {
            cursor: pointer;
            background-color: white;
        }
        #dlgPhoto .modal-body{
            text-align: center;
        }
        .preview{
 
            max-width: 500px;
        }
    </style>
</head>
<body>
 
<div class="container">
    <div class="row">
        <h1 style="text-align: center">Employee information form</h1>
        <div class="panel panel-default">
            <div class="clearfix panel-heading ">
                <div class="input-group" style="width: 500px;">
                    
                </div>
            </div>
 
            <table border=1 class="table table-bordered table-hover">
                <thead>
                <tr>
                    <th>Serial number</th>
                    <th>Employee number</th>
                    <th>full name</th>
                    <th>department</th>
                    <th>post</th>
                    <th>wages</th>
                    <th>&nbsp;</th>
                </tr>
                </thead>
                <tbody>
                <#-- employee_ The list value range is found from request, session and servletContext in turn -- >
                <#list employee_list as emp>
                <tr>
                    <td>${emp_index+1}</td>
                    <td>${emp.empno?string("0")}</td>
                    <td>${emp.ename}</td>
                    <td>${emp.department}</td>
                    <td>${emp.job}</td>
                    <td style="color: red;font-weight: bold">￥${emp.salary?string("0.00")}</td>
                    
                </tr>
                </#list>
  
                </tbody>
            </table>
        </div>
    </div>
</div>
 
</body>
</html>

Visit / list on the web page to forward the request to employee FTL displays web pages and dynamically binds background data

Keywords: Java Web Development FreeMarker

Added by cheese on Mon, 17 Jan 2022 06:26:14 +0200

Programming VIP

Template engine and Freemarker

Template engine and Freemarker

template engine

Mainstream template engine

Freemarker

JSP and Freemarker

Freemarker quick start

FTL value

Branch judgment

List, iteration list, Map

Built in function (common)

Freemarker and Servlet integration

Popular Keywords