使用Freemaker的示例(和servlet的搭配使用)

总体目录结构如下：

搭建完成后，效果和示例二是一样的。

1.新建项目FreemakerS ，将freemaker.jar 拷入lib下;
2.在新建com.shiryu.freeServlet.model包里新建以下文件：

实体类Guestbook.java

package com.shiryu.freeServlet.model;

public class Guestbook {
    private String name;
    private String email;
    private String message;

    public Guestbook(String name, String email, String message) {
        this.name = name;
        this.email = email;
        this.message = message;
    }

    public String getEmail() {
        return email;
    }

    public String getMessage() {
        return message;
    }

    public String getName() {
        return name;
    }
}

Page.java

//用来传递模板文件template或则是跳转forword
package com.shiryu.freeServlet.model;

import java.util.*;

public class Page {
    private String template;
    private String forward; 
    private Map root = new HashMap();
    
    //put具有四种形态，形参不同类型
    public void put(String name,Object value){
        root.put(name, value);
    }
    
    public void put(String name,int value){
        root.put(name, value);
    }
    
    public void put(String name,double value){
        root.put(name, value);
    }
    
    public void put(String name,boolean value){
        root.put(name, value);
    }

    public String getTemplate() {
        return template;
    }

    public void setTemplate(String template) {
        forward=null;
        this.template = template;
    }

    public String getForward() {
        return forward;
    }

    public void setForward(String forward) {
        template = null;
        this.forward = forward;
    }

    public Map getRoot() {
        return root;
    }
}

2.在新建com.shiryu.freeServlet.controller包下新建如下文件：

ControllerServlet.java

package com.shiryu.freeServlet.controller;

import java.io.*;
import java.lang.reflect.*;
import java.util.Locale;
import javax.servlet.*;
import javax.servlet.http.*;
import com.shiryu.freeServlet.model.Page;
import freemarker.template.*;

public class ControllerServlet extends HttpServlet {
    private static final long serialVersionUID = 2621960985463765229L;
    private Configuration cfg;

    public void init() {
        // 创建一个freemaker.template包中的configrution对象
        cfg = new Configuration();

       // 得到模板文件所在路径
        cfg.setServletContextForTemplateLoading(getServletContext(),"templates");

        // 将update dealy设置为0方便测试
        cfg.setTemplateUpdateDelay(0);

        // 在html错误被打印出来
        cfg.setTemplateExceptionHandler(TemplateExceptionHandler.HTML_DEBUG_HANDLER);

        // 使用beans封装应用
        cfg.setObjectWrapper(ObjectWrapper.BEANS_WRAPPER);

        cfg.setDefaultEncoding("UTF-8");

        cfg.setOutputEncoding("UTF-8");

        cfg.setLocale(Locale.getDefault());

    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)

            throws ServletException, IOException {

        // 对action进行选择
        String action = req.getServletPath();
        if (action == null)
            action = "index";
        if (action.startsWith("/"))

            //语法strVariable.substring(start, end)
            //substring（int i）他的意思是从字符串的索引值为i开始截取(获得)字符串
            action = action.substring(1);

        //int lastIndexOf(int ch, int fromIndex) 
//从指定的索引处开始进行后向搜索，返回最后一次出现的指定字符在此字符串中的索引。
        if (action.lastIndexOf(".") != -1) {
            action = action.substring(0, action.lastIndexOf("."));
        }
        Method actionMethod = null;

        //得到当前运行时对象所属的类对象，返回类对象的一个方法
        //参数为此方法的名称字符串及所需参数的类对象类型数组
try {
            actionMethod = getClass().getMethod(action + "Action", new Class[] { HttpServletRequest.class, Page.class });

        } catch (SecurityException e) {

            e.printStackTrace();

        } catch (NoSuchMethodException e) {

            e.printStackTrace();
        }
        req.setCharacterEncoding(cfg.getOutputEncoding());

        Page page = new Page();

        try {
            //方法调用，当前的对象数组
            //例如：
            //Class[] a=new Class[]{String[].class}; 
            //Object[] b=new Object[]{new String[0]}; 
            // 生成2个新的数组,第一个数组里存的是Class类型,第二个存放的是Object类型. 
            actionMethod.invoke(this, new Object[] { req, page });

        } catch (IllegalArgumentException e) {

            e.printStackTrace();

        } catch (IllegalAccessException e) {

            e.printStackTrace();

        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        // 如果从page获得了template，进行页面输出
        if (page.getTemplate() != null) {

            Template t = cfg.getTemplate(page.getTemplate());

            resp.setContentType("text/html; charset=" + cfg.getOutputEncoding());

            resp.setHeader("Cache-Control","no-store,no-cache,must-revalidate," + "post-check=0, 
pre-check=0");

            resp.setHeader("Pragma", "no-cache");

            resp.setHeader("Expires", "Thu, 01 Dec 2010 00:00:00 GMT");

            Writer out = resp.getWriter();

            try {

                t.process(page.getRoot(), out);

            } catch (TemplateException e) {
                e.printStackTrace();
            }
        }

        // 如果page的指向不为空
        else if (page.getForward() != null) {

            RequestDispatcher rd = req.getRequestDispatcher(page.getForward());

            rd.forward(req, resp);
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)

            throws ServletException, IOException {

        doGet(req, resp);
    }
}

GuestbookServlet.java

package com.shiryu.freeServlet.controller;

import java.io.IOException;
import java.util.*;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;

import com.shiryu.freeServlet.model.*;

public class GuestbookServlet extends ControllerServlet {

    private static final long serialVersionUID = 1385738680025723760L;

    @SuppressWarnings("unchecked")
    private ArrayList guestbooks = new ArrayList();

    //各个action及其业务逻辑
    @SuppressWarnings("unchecked")
    public void indexAction(HttpServletRequest req, Page p) {

        List snapShot;

        synchronized (guestbooks) {
            snapShot = (List) guestbooks.clone();
        }
        p.put("guestbooks", snapShot);

        p.setTemplate("index.ftl");
    }

    @SuppressWarnings("unchecked")
    public void formAction(HttpServletRequest req, Page p) throws IOException,
            ServletException {

        p.put("name", noNull(req.getParameter("name")));

        p.put("email", noNull(req.getParameter("email")));

        p.put("message", noNull(req.getParameter("message")));

        List errors = (List) req.getAttribute("errors");

        p.put("errors", errors == null ? new ArrayList() : errors);

        p.setTemplate("form.ftl");
    }

    @SuppressWarnings("unchecked")
    public void addAction(HttpServletRequest req, Page p) throws IOException,
            ServletException {

        List errors = new ArrayList();

        String name = req.getParameter("name");

        String email = req.getParameter("email");

        String message = req.getParameter("message");

        if (isBlank(name)) {
            errors.add("please enter your name");
        }
        if (isBlank(message)) {
            errors.add("please enter your message");
        }
        if (errors.isEmpty()) {
            if (email == null)
                email = "";

            Guestbook book = new Guestbook(name.trim(), email.trim(), message);
            synchronized (guestbooks) {
                guestbooks.add(0, book);
            }
            p.put("entry", book);
            p.setTemplate("add.ftl");
        }else{
            req.setAttribute("errors", errors);
            p.setForward("form.a");
        }
    }

    public static String noNull(String s) {
        return s == null ? "" : s;
    }

    public static boolean isBlank(String s) {
        return s == null || s.trim().length() == 0;
    }
}

3.编辑 web.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app
    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
    "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<display-name>Freemaker Servlet Application</display-name>
<servlet>
   <servlet-name>guestbook</servlet-name>
   <servlet-class>com.shiryu.freeServlet.controller.GuestbookServlet</servlet-class>
</servlet>

<servlet-mapping>
     <servlet-name>guestbook</servlet-name>
     <url-pattern>*.a</url-pattern>
</servlet-mapping>

</web-app>

4.以下是前webroot / template下的ftl文件：
lib下 common.ftl 

<#macro page title>
<html>
<head>
    <title>FreeMarker Example Web Application 2 - ${title?html}</title>
    <meta http-equiv="Content-type" content="text/html; charset=${.output_encoding}">
</head>
<body>
    <h1>${title?html}</h1>
    <hr>
    <#nested>
    <hr>
    <table border="0" cellspacing=0 cellpadding=0 width="100%">
      <tr valign="middle">
        <td align="left">
          <i>FreeMarker Example 2</i>
        <td align="right">
          <a href="http://freemarker.org"><img src="poweredby_ffffff.png" border=0></a>
    </table>
</body>
</html>
</#macro>

index.ftl

<#import "/lib/common.ftl" as com>
<#escape x as x?html>

<@com.page title="Index">
<a href="form.a">Add new message</a> | <a href="help.html">How this works?</a>

<#if guestbooks?size = 0>
    <p>No messages.
<#else>
    <p>The messages are:
    <table border=0 cellspacing=2 cellpadding=2 width="100%">
      <tr align=center valign=top>
        <th bgcolor="#C0C0C0">Name
        <th bgcolor="#C0C0C0">Message
      <#list guestbooks as e>
        <tr align=left valign=top>
          <td bgcolor="#E0E0E0">${e.name} <#if e.email?length != 0> (<a href="mailto:${e.email}">${e.email}</a>)</#if>
          <td bgcolor="#E0E0E0">${e.message}
      </#list>
    </table>
</#if>
</@com.page>

</#escape>

form.ftl

<#import "/lib/common.ftl" as com>
<#escape x as x?html>

<@com.page title="Add Entry">
   <!- - 错误的输出 - ->
<#if errors?size != 0>
    <p><font color=red>Please correct the following problems:</font>
    <ul>
      <#list errors as e>
        <li><font color=red>${e}</font>
      </#list>
    </ul>
</#if>

<form method="post" action="add.a">
     Your name: <input type="text" name="name" value="${name}" size=51><br>
     Your e-mail (optional): <input type="text" name="email" value="${email}" size=40><br>
     Message:<br> 
     <textarea name="message" wrap="soft" rows=3 cols=50>${message}</textarea><br>
     <input type="submit" value="Submit">
</form>
<p><a href="index.a">Back to the index page</a>
</@com.page>

</#escape>

add.ftl

<#import "/lib/common.ftl" as com>
<#escape x as x?html>

<@com.page title="Entry added">
<p>You have added the following entry to the guestbook:
<p><b>Name:</b> ${entry.name}
<#if entry.email?length != 0>
    <p><b>Email:</b> ${entry.email}
</#if>
<p><b>Message:</b> ${entry.message}
<p><a href="index.a">Back to the index page...</a>
</@com.page>

</#escape>