Freemarker入门案例(一)

首先需要到freemarker官方下载freemarker的jar包，导入到项目中，如：freemarker-2.3.19.jar

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1、先建个freemarker的工具类，FreemarkerUtil.java

package com.ljq.fm;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Map;

import freemarker.template.Configuration;
import freemarker.template.Template;
import freemarker.template.TemplateException;

public class FreemarkerUtil {

    public Template getTemplate(String name) {
        try {
            // 通过Freemaker的Configuration读取相应的ftl
            Configuration cfg = new Configuration();
            // 设定去哪里读取相应的ftl模板文件
            cfg.setClassForTemplateLoading(this.getClass(), "/ftl");
            // 在模板文件目录中找到名称为name的文件
            Template temp = cfg.getTemplate(name);
            return temp;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 控制台输出
     * 
     * @param name
     * @param root
     */
    public void print(String name, Map<String, Object> root) {
        try {
            // 通过Template可以将模板文件输出到相应的流
            Template temp = this.getTemplate(name);
            temp.process(root, new PrintWriter(System.out));
        } catch (TemplateException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 输出HTML文件
     * 
     * @param name
     * @param root
     * @param outFile
     */
    public void fprint(String name, Map<String, Object> root, String outFile) {
        FileWriter out = null;
        try {
            // 通过一个文件输出流，就可以写到相应的文件中，此处用的是绝对路径
            out = new FileWriter(new File("E:/workspace/freemarkprj/page/" + outFile));
            Template temp = this.getTemplate(name);
            temp.process(root, out);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (TemplateException e) {
            e.printStackTrace();
        } finally {
            try {
                if (out != null)
                    out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

2 、在src目录下建个ftl包，用于存放ftl模板文件，this.getClass() 就是根据当前类的路径获取模板文件位置
01.ftl

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>测试</title>
</head>

<body>
<h1>你好${username}</h1>
</body>
</html>

02.ftl

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>

<body>
<h1>你好： ${username}</h1>
</body>
</html>

03.ftl

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>${user.id}-----${user.name}-----${user.age}</h1>
<#if user.age lt 12>
    ${user.name}还是一个小孩
<#elseif user.age lt 18>
    ${user.name}快成年
<#else>
    ${user.name}已经成年
</#if>
</body>
</html>

04.ftl

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<#list users as user>
${user.id}---------${user.name}-------${user.age}<br/>
</#list>
</body>
</html>

05.ftl

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>

<body>
<hr/>
<#list users as user>
${user.id}---------${user.name}-------${user.age}<br/>
</#list>
</body>
</html>

06.ftl

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>

<body>
${user.id}-------${user.name}------${user.group!}  <#-- !后为空就不输出  -->
<#--${user.group.name!}--><#-- 按照以上的方式加! freemarker仅仅只会判断group.name是不是空值 -->
${(user.group.name)!"1234"} 

${(a.b)!"没有a.b元素"}

<#--
!:指定缺失变量的默认值 
??:判断某个变量是否存在,返回boolean值 
-->
<#if (a.b)??> <#--if后不用加$-->
    不为空
<#else>
    为空
</#if>
</body>
</html>

实体类User.java

package com.ljq.fm;

import java.io.Serializable;

@SuppressWarnings("serial")
public class User implements Serializable {
    private int id;
    private String name;
    private int age;
    private Group group;

    public Group getGroup() {
        return group;
    }

    public void setGroup(Group group) {
        this.group = group;
    }

    public User() {
    }

    public User(int id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

}

实体类Group.java

package com.ljq.fm;

/**
 * 
 * 
 * @author 林计钦
 * @version 1.0 2013-10-25 下午02:36:09
 */
public class Group {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

3、再建个Junit的测试类 FreemarkerTest.java

package com.freemarker;


import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


import com.freemarker.dto.Group;
import com.freemarker.dto.User;


public class FreemarkerTest {

	public static void main(String[] args) {
		Map<String, Object> root = new HashMap<String, Object>();
		root.put("username", "王风");//在ftl中要赋值的变量
		root.put("user", new User(1,"name1",11,new Group("组1")));
		List<User> users = new ArrayList<User>();
		users.add(new User(1,"name1",11));
		users.add(new User(2,"name2",15));
		users.add(new User(3,"name3",20));
		users.add(new User(4,"name4",30));
		root.put("users", users);
		
		FreeMarkerUtil util = new FreeMarkerUtil();
		util.fprint("001.jsp", root, "0001.jsp");
		
		util.fprint("01.ftl", root, "01.html");
		util.fprint("02.ftl", root, "02.html");
		util.fprint("03.ftl", root, "03.html");
		util.fprint("04.ftl", root, "04.html");
		util.fprint("05.ftl", root, "05.html");
		util.fprint("06.ftl", root, "06.html");			
	}	
}