【Velocity四】Velocity与Java互操作

石可破，丹可磨

【Velocity四】Velocity与Java互操作
Java / 管理员发布于 2021-04-30 17:03:33 12

Velocity出现的目的用于简化基于MVC的web应用开发，用于替代JSP标签技术，那么Velocity如何访问Java代码.本篇继续以Velocity三http://bit1129.iteye.com/blog/2106142中的例子为基础，

POJO

package com.tom.servlets;public class User {    private String name;    private String passwd;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getPasswd() {        return passwd;    }    public void setPasswd(String passwd) {        this.passwd = passwd;    }}

Service

package com.tom.servlets;public class UserService {    public User get(String userId) {        User user = new User();        user.setName("tom");        user.setPasswd("tom_pwd");        return user;    }    public User get(Long userId) {        User user = new User();        user.setName("Jack");        user.setPasswd("Jack");        return user;    }        public void save() {//用于测试,vm是否可以调用无参数的方法        System.out.println("save is called");    }}

Servlet代码

package com.tom.servlets;import org.apache.velocity.Template;import org.apache.velocity.context.Context;import org.apache.velocity.tools.view.VelocityViewServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class TestVelocityViewServlet extends VelocityViewServlet {    @Override    protected Template handleRequest(HttpServletRequest request, HttpServletResponse response, Context ctx) {        UserService userService = new UserService();        ctx.put("userService" , userService);//把userService对象设置到Context中        return getTemplate("obj.vm");    }}

vm代码

<!--obj.vm--><html>    <body>        <p>$userService</p> ##call userService's toString method        #set($user = $userService.get(0)) ##When call the java method on its object, only string typed parameters can be accepted        <p>$user.name</p> ##print #$user.name as it is, because $user can't be resolved        <p>$user.getName()</p> ##Equivalent with $user.name        #set($user = $userService.get("0"))        <p>$user.name</p> ##print $$user.name as it is, because $user can't be resolved        <p>$user.getName()</p> ##Equivalent with $user.name        <p>$user.save()</p> ##$user.save can't be resolved,so vm can't resolve method that takes no parameter    </body></html>