Spring Boot 整合视图层技术

  • 2019 年 10 月 7 日
  • 笔记

这一节我们主要学习如何整合视图层技术：

  • Jsp
  • Freemarker
  • Thymeleaf

在之前的案例中，我们都是通过 @RestController 来处理请求，所以返回的内容为json对象。那么如果需要渲染html页面的时候，要如何实现呢？

　　Spring Boot推荐使用模板引擎

　　模板引擎实现伪html 达到seo优化 使动态页面静态化

　　在动态html上实现Spring Boot依然可以完美胜任，并且提供了多种模板引擎的默认配置支持，所以在推荐的模板引擎下，我们可以很快的上手开发动态网站。

　　Spring Boot提供了默认配置的模板引擎主要有以下几种：

　　　　Thymeleaf

　　　　FreeMarker

　　　　Velocity

　　　　Groovy

　　　　Mustache

　　Spring Boot建议使用这些模板引擎，避免使用jsp。

Jsp

创建项目

　　创建 war 项目，编写pom.xml

<?xml version="1.0" encoding="UTF-8"?>    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"           xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">      <modelVersion>4.0.0</modelVersion>        <groupId>com.springboot</groupId>      <artifactId>springboot-view</artifactId>      <version>1.0-SNAPSHOT</version>      <packaging>war</packaging>        <name>springboot-view Maven Webapp</name>      <!-- FIXME change it to the project's website -->      <url>http://www.example.com</url>        <properties>          <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>          <maven.compiler.source>1.8</maven.compiler.source>          <maven.compiler.target>1.8</maven.compiler.target>      </properties>        <parent>          <groupId>org.springframework.boot</groupId>          <artifactId>spring-boot-starter-parent</artifactId>          <version>2.1.6.RELEASE</version>      </parent>        <dependencies>          <!-- Web 组件 -->          <dependency>              <groupId>org.springframework.boot</groupId>              <artifactId>spring-boot-starter-web</artifactId>          </dependency>          <!-- Spring Boot不推荐使用 jsp，所以需要手动导入 jstl 和 jasper 依赖 -->          <!-- jstl -->          <dependency>              <groupId>javax.servlet</groupId>              <artifactId>jstl</artifactId>          </dependency>          <!-- jasper -->          <dependency>              <groupId>org.apache.tomcat.embed</groupId>              <artifactId>tomcat-embed-jasper</artifactId>              <scope>provided</scope>          </dependency>      </dependencies>  </project>

视图解析器

　　resources/application.properties

spring.mvc.view.prefix=/WEB-INF/jsp/  spring.mvc.view.suffix=.jsp

实体类

　　User.java

package com.springboot.pojo;    import java.io.Serializable;    public class User implements Serializable {        private Integer id;      private String username;      private Integer age;        public User() {      }        public User(Integer id, String username, Integer age) {          this.id = id;          this.username = username;          this.age = age;      }        public Integer getId() {          return id;      }        public void setId(Integer id) {          this.id = id;      }        public String getUsername() {          return username;      }        public void setUsername(String username) {          this.username = username;      }        public Integer getAge() {          return age;      }        public void setAge(Integer age) {          this.age = age;      }        @Override      public String toString() {          return "User{" +                  "id=" + id +                  ", username='" + username + ''' +                  ", age=" + age +                  '}';      }    }

控制层

　　UserController.java

package com.springboot.controller;    import com.springboot.pojo.User;  import org.springframework.stereotype.Controller;  import org.springframework.ui.Model;  import org.springframework.web.bind.annotation.RequestMapping;    import java.util.ArrayList;  import java.util.List;    @Controller  public class UserController {        @RequestMapping("/showUser")      public String showUser(Model model) {          List<User> list = new ArrayList<>();          list.add(new User(1, "张三", 18));          list.add(new User(2, "李四", 20));          list.add(new User(3, "王五", 22));          model.addAttribute("list", list);          // 跳转视图          return "userList";      }    }

视图层

　　userList.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>  <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>  <!DOCTYPE html>  <html>  <head>      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">      <title>用户展示</title>  </head>  <body>      <table border="1" cellspacing="0" align="center" width="50%">          <tr>              <th>ID</th>              <th>Name</th>              <th>Age</th>          </tr>          <c:forEach items="${list}" var="user">              <tr>                  <td>${user.id}</td>                  <td>${user.username}</td>                  <td>${user.age}</td>              </tr>          </c:forEach>      </table>  </body>  </html>

启动类

　　App.java

package com.springboot;    import org.springframework.boot.SpringApplication;  import org.springframework.boot.autoconfigure.SpringBootApplication;    @SpringBootApplication  public class App {        public static void main(String[] args) {          SpringApplication.run(App.class, args);      }    }

　　结果

Freemarker

创建项目

　　创建 war 项目，编写pom.xml

<?xml version="1.0" encoding="UTF-8"?>    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"           xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">      <modelVersion>4.0.0</modelVersion>        <groupId>com.springboot</groupId>      <artifactId>springboot-view</artifactId>      <version>1.0-SNAPSHOT</version>      <packaging>war</packaging>        <name>springboot-view Maven Webapp</name>      <!-- FIXME change it to the project's website -->      <url>http://www.example.com</url>        <properties>          <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>          <maven.compiler.source>1.8</maven.compiler.source>          <maven.compiler.target>1.8</maven.compiler.target>      </properties>        <parent>          <groupId>org.springframework.boot</groupId>          <artifactId>spring-boot-starter-parent</artifactId>          <version>2.1.6.RELEASE</version>      </parent>        <dependencies>          <!-- web 组件 -->          <dependency>              <groupId>org.springframework.boot</groupId>              <artifactId>spring-boot-starter-web</artifactId>          </dependency>          <!-- freemarker 组件 -->          <dependency>              <groupId>org.springframework.boot</groupId>              <artifactId>spring-boot-starter-freemarker</artifactId>          </dependency>      </dependencies>  </project>

视图解析器

　　该文件内容不一定非得需要，可以不添加，不添加使用默认值。

　　resources/application.properties

# FREEMARKER (FreeMarkerAutoConfiguration)  spring.freemarker.allow-request-override=false  spring.freemarker.allow-session-override=false  spring.freemarker.cache=true  spring.freemarker.charset=UTF-8  spring.freemarker.check-template-location=true  spring.freemarker.content-type=text/html  spring.freemarker.enabled=true  spring.freemarker.expose-request-attributes=false  spring.freemarker.expose-session-attributes=false  spring.freemarker.expose-spring-macro-helpers=true  spring.freemarker.prefer-file-system-access=true  spring.freemarker.suffix=.ftl  spring.freemarker.template-loader-path=classpath:/templates/  spring.freemarker.settings.template_update_delay=0  spring.freemarker.settings.default_encoding=UTF-8  spring.freemarker.settings.classic_compatible=true  spring.freemarker.order=1

实体类

　　User.java

package com.springboot.pojo;    import java.io.Serializable;    public class User implements Serializable {        private Integer id;      private String username;      private Integer age;        public User() {      }        public User(Integer id, String username, Integer age) {          this.id = id;          this.username = username;          this.age = age;      }        public Integer getId() {          return id;      }        public void setId(Integer id) {          this.id = id;      }        public String getUsername() {          return username;      }        public void setUsername(String username) {          this.username = username;      }        public Integer getAge() {          return age;      }        public void setAge(Integer age) {          this.age = age;      }        @Override      public String toString() {          return "User{" +                  "id=" + id +                  ", username='" + username + ''' +                  ", age=" + age +                  '}';      }    }

控制层

　　UserController.java

package com.springboot.controller;    import com.springboot.pojo.User;  import org.springframework.stereotype.Controller;  import org.springframework.ui.Model;  import org.springframework.web.bind.annotation.RequestMapping;    import java.util.ArrayList;  import java.util.List;    @Controller  public class UserController {        @RequestMapping("/showUser")      public String showUser(Model model) {          List<User> list = new ArrayList<>();          list.add(new User(1, "张三", 18));          list.add(new User(2, "李四", 20));          list.add(new User(3, "王五", 22));          model.addAttribute("list", list);          // 跳转视图          return "userList";      }    }

视图层

　　Spring Boot要求模板形式的视图层技术的文件必须要放到 src/main/resources 目录下的 templates 目录。

　　该目录内的模板文件名称必须是 ftl 的后缀结尾。

　　userList.ftl

<!DOCTYPE html>  <html>  <head>      <title>用户展示</title>      <meta charset="UTF-8"></meta>  </head>  <body>      <table border="1" cellspacing="0" align="center" width="50%">          <tr>              <th>ID</th>              <th>Name</th>              <th>Age</th>          </tr>          <#list list as user >              <tr>                  <td>${user.id}</td>                  <td>${user.username}</td>                  <td>${user.age}</td>              </tr>          </#list>      </table>  </body>  </html>

启动类

　　App.java

package com.springboot;    import org.springframework.boot.SpringApplication;  import org.springframework.boot.autoconfigure.SpringBootApplication;    @SpringBootApplication  public class App {        public static void main(String[] args) {          SpringApplication.run(App.class, args);      }    }

　　结果

Thymeleaf （重点讲解）

入门案例

创建项目

　　创建 war 项目，编写pom.xml

<?xml version="1.0" encoding="UTF-8"?>    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"           xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">      <modelVersion>4.0.0</modelVersion>        <groupId>com.springboot</groupId>      <artifactId>springboot-view</artifactId>      <version>1.0-SNAPSHOT</version>      <packaging>war</packaging>        <name>springboot-view Maven Webapp</name>      <!-- FIXME change it to the project's website -->      <url>http://www.example.com</url>        <properties>          <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>          <maven.compiler.source>1.8</maven.compiler.source>          <maven.compiler.target>1.8</maven.compiler.target>      </properties>        <parent>          <groupId>org.springframework.boot</groupId>          <artifactId>spring-boot-starter-parent</artifactId>          <version>2.1.6.RELEASE</version>      </parent>        <dependencies>          <!-- web 组件 -->          <dependency>              <groupId>org.springframework.boot</groupId>              <artifactId>spring-boot-starter-web</artifactId>          </dependency>          <!-- thymeleaf 组件 -->          <dependency>              <groupId>org.springframework.boot</groupId>              <artifactId>spring-boot-starter-thymeleaf</artifactId>          </dependency>      </dependencies>  </project>

控制层

　　ThymeleafController.java

package com.springboot.controller;    import org.springframework.stereotype.Controller;  import org.springframework.ui.Model;  import org.springframework.web.bind.annotation.RequestMapping;    @Controller  public class ThymeleafController {        @RequestMapping("/show")      public String showMsg(Model model) {          model.addAttribute("msg", "Thymeleaf 入门案例");          return "msg";      }    }

视图层

　　Spring Boot要求模板形式的视图层技术的文件必须要放到 src/main/resources 目录下的 templates 目录。

　　msg.html

<!DOCTYPE html>  <html lang="en">  <head>      <meta charset="UTF-8">      <title>Thymeleaf</title>  </head>  <body>      <span th:text="Thymeleaf"></span>      <hr/>      <span th:text="${msg}"></span>  </body>  </html>

启动类

　　App.java

package com.springboot;    import org.springframework.boot.SpringApplication;  import org.springframework.boot.autoconfigure.SpringBootApplication;    @SpringBootApplication  public class App {        public static void main(String[] args) {          SpringApplication.run(App.class, args);      }    }

　　运行结果出现异常（如果是 Spring Boot 1.X.X 版本才会出现此异常）：

org.xml.sax.SAXParseException: 元素类型 "meta" 必须由匹配的结束标记 "</meta>" 终止。

异常处理

　　如果是 Spring Boot 1.X.X 版本需要以下操作，本案例是 Spring Boot 2.1.6 版本，所以不需要更改。

方式一：编写风格严谨的HTML代码

<meta charset="UTF-8"/>

方式二：更换Thymeleaf的jar包版本

　　thymeleaf.jar：更新为 3.0 以上的版本

<img src="https://mrhelloworld.oss-cn-shanghai.aliyuncs.com/articlesImages/1562659063590.png"/

<properties>      <thymeleaf.version>3.0.11.RELEASE</thymeleaf.version>  </properties>

运行结果

Thymeleaf 语法详解

Thymeleaf 内置对象语法：

  • 调用内置对象一定要用 #
  • 大部分的内置对象都以 s 结尾 strings、numbers、dates

准备数据

实体类

　　User.java

package com.springboot.pojo;    import java.io.Serializable;    public class User implements Serializable {        private Integer id;      private String username;      private Integer age;        public User() {      }        public User(Integer id, String username, Integer age) {          this.id = id;          this.username = username;          this.age = age;      }        public Integer getId() {          return id;      }        public void setId(Integer id) {          this.id = id;      }        public String getUsername() {          return username;      }        public void setUsername(String username) {          this.username = username;      }        public Integer getAge() {          return age;      }        public void setAge(Integer age) {          this.age = age;      }        @Override      public String toString() {          return "User{" +                  "id=" + id +                  ", username='" + username + ''' +                  ", age=" + age +                  '}';      }    }

控制层

　　ThymeleafController.java

package com.springboot.controller;    import com.springboot.pojo.User;  import org.springframework.stereotype.Controller;  import org.springframework.ui.Model;  import org.springframework.web.bind.annotation.PathVariable;  import org.springframework.web.bind.annotation.RequestMapping;    import javax.servlet.http.HttpServletRequest;  import javax.servlet.http.HttpServletResponse;  import java.util.*;    @Controller  public class ThymeleafController {        @RequestMapping("/show")      public String showMsg(Model model,                            HttpServletRequest request,                            HttpServletResponse response) {            // 字符串          model.addAttribute("msg", "Thymeleaf 入门案例");          // 日期时间          model.addAttribute("myDate", new Date());          // 条件判断if          model.addAttribute("sex", 1);          // 条件判断switch          model.addAttribute("id", 1);          // 对象          model.addAttribute("user", new User(1, "张三", 20));            // 迭代遍历list          List<User> userList = new ArrayList<>();          userList.add(new User(1, "张三", 20));          userList.add(new User(2, "李四", 22));          userList.add(new User(3, "王五", 24));          model.addAttribute("userList", userList);            // 迭代遍历map          Map<String, User> userMap = new HashMap<>();          userMap.put("u1", new User(1, "张三", 20));          userMap.put("u2", new User(2, "李四", 22));          userMap.put("u3", new User(3, "王五", 24));          model.addAttribute("userMap", userMap);            // 域对象操作          request.setAttribute("req", "HttpServletRequest");          request.getSession().setAttribute("sess", "HttpSession");          request.getSession().getServletContext().setAttribute("app", "Application");          return "msg";        }        /**       * URL表达式-相对路径       * @return       */      @RequestMapping("/index")      public String index() {          return "index";      }        /**       * URL表达式-普通传参       * @param id       * @param username       * @return       */      @RequestMapping("/user")      public String user(Integer id, String username) {          System.out.println("id：" + id + " username：" + username);          return "user";      }        /**       * URL表达式-restful传参       * @param id       * @param username       * @return       */      @RequestMapping("/person/{id}/{username}")      public String person(@PathVariable Integer id, @PathVariable String username) {          System.out.println("id：" + id + " username：" + username);          return "person";      }    }

视图层

　　index.html

<!DOCTYPE html>  <html lang="en">  <head>      <meta charset="UTF-8">      <title>Thymeleaf</title>  </head>  <body>      index  </body>  </html>

　　user.html

<!DOCTYPE html>  <html lang="en">  <head>      <meta charset="UTF-8">      <title>Thymeleaf</title>  </head>  <body>      user  </body>  </html>

　　person.html

<!DOCTYPE html>  <html lang="en">  <head>      <meta charset="UTF-8">      <title>Thymeleaf</title>  </head>  <body>      person  </body>  </html>

字符串

变量输出

th:text：在页面中输入值

<span th:text="Thymeleaf"></span>

th:value：可以将一个值设置至input标签的value中

<input type="text" th:value="${msg}" />

字符串操作

${#strings.isEmpty(key)}：判断字符串是否为空

<span th:text="${#strings.isEmpty(msg)}"></span>

${#strings.contains(msg, 'T')}：判断字符串是否包含子串

<span th:text="${#strings.contains(msg, 'T')}"></span>

${#strings.startsWith(msg, 'T')}：判断字符串是否以子串开头

<span th:text="${#strings.startsWith(msg, 'T')}"></span>

${#strings.endsWith(msg, 'T')}：判断字符串是否以子串结尾

<span th:text="${#strings.endsWith(msg, 'T')}"></span>

${#strings.length(msg)}：返回字符串的长度

<span th:text="${#strings.length(msg)}"></span>

${#strings.indexOf(msg, 'T')}：查找子串的位置，并返回该子串的下标，如果没找到则返回-1

<span th:text="${#strings.indexOf(msg, 'T')}"></span>

${#strings.substring(msg, 5)}：截取子串，从指定下标开始截止到末尾结束

${#strings.substring(msg, 5, 12)}：截取子串，从指定下标开始截止到指定下标结束

<span th:text="${#strings.substring(msg, 5)}"></span>  <span th:text="${#strings.substring(msg, 5, 12)}"></span>

${#strings.toUpperCase(msg)}：将字符串转大写

<span th:text="${#strings.toUpperCase(msg)}"></span>

${#strings.toLowerCase(msg)}：将字符串转小写

<span th:text="${#strings.toLowerCase(msg)}"></span>

日期时间

${#dates.format(key)}：格式化日期，以浏览器默认语言为格式化标准

<span th:text="${#dates.format(myDate)}"></span>

${#dates.format(key,'yyy/MM/dd')}：自定义格式日期转换

<span th:text="${#dates.format(myDate, 'yyyy年MM月dd日 HH:mm:ss')}"></span>

${#dates.year(myDate)}：获取年份，还可以获取月份、日、时、分、秒

<span th:text="${#dates.year(myDate)}"></span>年  <span th:text="${#dates.month(myDate)}"></span>月  <span th:text="${#dates.day(myDate)}"></span>日  <span th:text="${#dates.hour(myDate)}"></span>时  <span th:text="${#dates.minute(myDate)}"></span>分  <span th:text="${#dates.second(myDate)}"></span>秒

条件判断

th:if：单选择

性别：<span th:if="${sex} == 1">男</span>       <span th:if="${sex} == 2">女</span>

th:switch：多选择（如果要实现 if else if else 判断表达式，在 Thymeleaf 要使用 th:switch 代替）

编号：<span th:switch="${id}">          <span th:case="1">1 张三</span>          <span th:case="2">2 李四</span>          <span th:case="3">3 王五</span>      </span>

对象

<input th:value="${user.username}"/>  <span th:text="${user.age}"></span>

迭代遍历

th:each：迭代遍历

<table border="1" cellspacing="0">      <tr>          <th>ID</th>          <th>NAME</th>          <th>AGE</th>      </tr>      <tr th:each="user : ${userList}">          <td th:text="${user.id}"></td>          <td th:text="${user.username}"></td>          <td th:text="${user.age}"></td>      </tr>  </table>

th:each：状态变量属性

  • index：当前迭代器的索引 从 0 开始
  • count：当前迭代对象的计数 从 1 开始
  • size：被迭代对象的长度
  • even/odd：布尔值，当前循环是否是偶数/奇数 从 0 开始
  • first：布尔值，当前循环的是否是第一条，如果是返回 true 否则返回 false
  • last：布尔值，当前循环的是否是最后一条，如果是则返回 true 否则返回 false
<table border="1" cellspacing="0">      <tr>          <th>Id</th>          <th>Name</th>          <th>Age</th>          <th>Index</th>          <th>Count</th>          <th>Size</th>          <th>Even</th>          <th>Odd</th>          <th>First</th>          <th>Last</th>      </tr>      <tr th:each="user, state : ${userList}">          <td th:text="${user.id}"></td>          <td th:text="${user.username}"></td>          <td th:text="${user.age}"></td>          <td th:text="${state.index}"></td>          <td th:text="${state.count}"></td>          <td th:text="${state.size}"></td>          <td th:text="${state.even}"></td>          <td th:text="${state.odd}"></td>          <td th:text="${state.first}"></td>          <td th:text="${state.last}"></td>      </tr>  </table>

th:each：迭代 Map

<table border="1" cellspacing="0">      <tr>          <th>Id</th>          <th>Name</th>          <th>Age</th>      </tr>      <tr th:each="user : ${userMap}">          <td th:text="${user}"></td>      </tr>  </table>  <table border="1" cellspacing="0">      <tr>          <th>Id</th>          <th>Name</th>          <th>Age</th>      </tr>      <tr th:each="user : ${userMap}">          <td th:each="entry : ${user}" th:text="${entry.value.id}" ></td>          <td th:each="entry : ${user}" th:text="${entry.value.username}"></td>          <td th:each="entry : ${user}" th:text="${entry.value.age}"></td>      </tr>  </table>

<img src="https://mrhelloworld.oss-cn-shanghai.aliyuncs.com/articlesImages/1562747209340.png"/

域对象操作

${#httpServletRequest.getAttribute(key)}：HttpServletRequest

Request：<span th:text="${#httpServletRequest.getAttribute('req')}"></span>

${session.key}：HttpSession

Session：<span th:text="${session.sess}"></span>

${application.key}：ServletContext

Application：<span th:text="${application.app}"></span>

URL表达式

基本语法

URL表达式的基本语法：@{}

th:href：绝对路径

<a th:href="@{http://www.baidu.com}">绝对路径</a>

th:href：相对路径，相对于当前项目的根路径

<a th:href="@{/index}">相对于当前项目的根路径</a>

th:href：相对路径， 相对于服务器的根路径

<a th:href="@{~/project/resourcename}">相对于服务器的根路径</a>

参数传递

<a th:href="@{/user(id=1, username=zhagnsan)}">相对路径-普通传参</a>  <a th:href="@{/person/1/zhangsan}">相对路径-restful传参</a>  <a th:href="@{/person/{id}/{name}(id=2, name=lisi)}">相对路径-restful传参</a>

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