模板引擎
springboot我们目前是以jar包的形式打包,实际上我们之前是打成war包,放到tomcat服务器里面,可以用JSP。
但是jar包就导致不能用JSP,换一种方式就是springboot推荐的Thymeleaf模板引擎(JSP也是一种模板引擎,除此之外还有什么framework也是一种模板引擎),
什么是模板引擎?
模板引擎就是解决我们需要动态赋值给前端的一种解决方案
(模板引擎的作用就是我们来写一个页面模板,比如有些值呢,是动态的,我们写一些表达式。而这些值,从哪来呢,就是我们在后台封装一些数据。然后把这个模板和这个数据交给我们模板引擎,模板引擎按照我们这个数据帮你把这表达式解析、填充到我们指定的位置,然后把这个数据最终生成一个我们想要的内容给我们写出去,这就是我们这个模板引擎,不管是jsp还是其他模板引擎,都是这个思想。只不过呢,就是说不同模板引擎之间,他们可能这个语法有点不一样。其他的我就不介绍了,我主要来介绍一下SpringBoot给我们推荐的Thymeleaf模板引擎,这模板引擎呢,是一个高级语言的模板引擎,他的这个语法更简单。而且呢,功能更强大。)
模板引擎的原理
引入Thymeleaf
引入就是导入依赖,以下是网址是相关的地址
Thymeleaf 官网:https://www.thymeleaf.org/
Thymeleaf 在Github 的主页:https://github.com/thymeleaf/thymeleaf
Spring官方文档:找到我们对应的版本
https://docs.spring.io/spring-boot/docs/2.2.5.RELEASE/reference/htmlsingle/#using-boot-starter
找到对应的pom依赖:可以适当点进源码看下本来的包!
<!--thymeleaf-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
Thymeleaf分析
Thymeleaf的引入依赖文件ThymeleafProperties,文件内容如下:
// IntelliJ API Decompiler stub source generated from a class file
// Implementation of methods is not available
package org.springframework.boot.autoconfigure.thymeleaf;
@org.springframework.boot.context.properties.ConfigurationProperties(prefix = "spring.thymeleaf")
public class ThymeleafProperties {
private static final java.nio.charset.Charset DEFAULT_ENCODING;
public static final java.lang.String DEFAULT_PREFIX = "classpath:/templates/";
public static final java.lang.String DEFAULT_SUFFIX = ".html";
private boolean checkTemplate;
private boolean checkTemplateLocation;
private java.lang.String prefix;
private java.lang.String suffix;
private java.lang.String mode;
private java.nio.charset.Charset encoding;
private boolean cache;
private java.lang.Integer templateResolverOrder;
private java.lang.String[] viewNames;
private java.lang.String[] excludedViewNames;
private boolean enableSpringElCompiler;
private boolean renderHiddenMarkersBeforeCheckboxes;
private boolean enabled;
private final org.springframework.boot.autoconfigure.thymeleaf.ThymeleafProperties.Servlet servlet;
private final org.springframework.boot.autoconfigure.thymeleaf.ThymeleafProperties.Reactive reactive;
public ThymeleafProperties() { }
public boolean isEnabled() { }
public void setEnabled(boolean enabled) { }
public boolean isCheckTemplate() { }
public void setCheckTemplate(boolean checkTemplate) { }
public boolean isCheckTemplateLocation() { }
public void setCheckTemplateLocation(boolean checkTemplateLocation) { }
public java.lang.String getPrefix() { }
public void setPrefix(java.lang.String prefix) { }
public java.lang.String getSuffix() { }
public void setSuffix(java.lang.String suffix) { }
public java.lang.String getMode() { }
public void setMode(java.lang.String mode) { }
public java.nio.charset.Charset getEncoding() { }
public void setEncoding(java.nio.charset.Charset encoding) { }
public boolean isCache() { }
public void setCache(boolean cache) { }
public java.lang.Integer getTemplateResolverOrder() { }
public void setTemplateResolverOrder(java.lang.Integer templateResolverOrder) { }
public java.lang.String[] getExcludedViewNames() { }
public void setExcludedViewNames(java.lang.String[] excludedViewNames) { }
public java.lang.String[] getViewNames() { }
public void setViewNames(java.lang.String[] viewNames) { }
public boolean isEnableSpringElCompiler() { }
public void setEnableSpringElCompiler(boolean enableSpringElCompiler) { }
public boolean isRenderHiddenMarkersBeforeCheckboxes() { }
public void setRenderHiddenMarkersBeforeCheckboxes(boolean renderHiddenMarkersBeforeCheckboxes) { }
public org.springframework.boot.autoconfigure.thymeleaf.ThymeleafProperties.Reactive getReactive() { }
public org.springframework.boot.autoconfigure.thymeleaf.ThymeleafProperties.Servlet getServlet() { }
public static class Reactive {
private org.springframework.util.unit.DataSize maxChunkSize;
private java.util.List<org.springframework.http.MediaType> mediaTypes;
private java.lang.String[] fullModeViewNames;
private java.lang.String[] chunkedModeViewNames;
public Reactive() { }
public java.util.List<org.springframework.http.MediaType> getMediaTypes() { }
public void setMediaTypes(java.util.List<org.springframework.http.MediaType> mediaTypes) { }
public org.springframework.util.unit.DataSize getMaxChunkSize() { }
public void setMaxChunkSize(org.springframework.util.unit.DataSize maxChunkSize) { }
public java.lang.String[] getFullModeViewNames() { }
public void setFullModeViewNames(java.lang.String[] fullModeViewNames) { }
public java.lang.String[] getChunkedModeViewNames() { }
public void setChunkedModeViewNames(java.lang.String[] chunkedModeViewNames) { }
}
public static class Servlet {
private org.springframework.util.MimeType contentType;
private boolean producePartialOutputWhileProcessing;
public Servlet() { }
public org.springframework.util.MimeType getContentType() { }
public void setContentType(org.springframework.util.MimeType contentType) { }
public boolean isProducePartialOutputWhileProcessing() { }
public void setProducePartialOutputWhileProcessing(boolean producePartialOutputWhileProcessing) { }
}
我们可以在其中看到默认的前缀和后缀。
我们只需要把我们的html页面放在类路径下的templates下,thymeleaf就可以帮我们自动渲染了。
启动访问结果
Thymeleaf 语法学习
要学习语法,还是参考官网文档最为准确,我们找到对应的版本看一下;
Thymeleaf 官网:https://www.thymeleaf.org/ , 简单看一下官网!我们去下载Thymeleaf的官方文档!
做一个最简单的向页面传值操作
(1)写一个页面,一个msg来作为传值
<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>ZP</title>
</head>
<body>
<h1>测试页面</h1>
<!--th:text就是将div中的内容设置为它指定的值,和之前学习的Vue一样-->
<div th:text="${msg}"></div>
</body>
</html>
代码
注意这里return的字符串要和上面的templates下面的html文件名字相同。
package com.example.zpspringboot3.controller;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
public class TestController {
// @RequestMapping("/t1")
// public String test1(){
// //classpath:/templates/test.html
// return "text";
// }
@RequestMapping("/t1")
public String test1(Model model){
//存入数据
model.addAttribute("msg","Hello,Thymeleaf");
//classpath:/templates/test.html
return "text2";
}
}
测试
通过thymeleaf官网文档学习一些语法:
1、我们可以使用任意的 th:attr 来替换Html中原生属性的值!
2、我们能写哪些表达式呢?
Simple expressions:(表达式语法)
Variable Expressions: ${...}:获取变量值;OGNL;
1)、获取对象的属性、调用方法
2)、使用内置的基本对象:#18
#ctx : the context object.
#vars: the context variables.
#locale : the context locale.
#request : (only in Web Contexts) the HttpServletRequest object.
#response : (only in Web Contexts) the HttpServletResponse object.
#session : (only in Web Contexts) the HttpSession object.
#servletContext : (only in Web Contexts) the ServletContext object.
3)、内置的一些工具对象:
#execInfo : information about the template being processed.
#uris : methods for escaping parts of URLs/URIs
#conversions : methods for executing the configured conversion service (if any).
#dates : methods for java.util.Date objects: formatting, component extraction, etc.
#calendars : analogous to #dates , but for java.util.Calendar objects.
#numbers : methods for formatting numeric objects.
#strings : methods for String objects: contains, startsWith, prepending/appending, etc.
#objects : methods for objects in general.
#bools : methods for boolean evaluation.
#arrays : methods for arrays.
#lists : methods for lists.
#sets : methods for sets.
#maps : methods for maps.
#aggregates : methods for creating aggregates on arrays or collections.
==================================================================================
Selection Variable Expressions: *{...}:选择表达式:和${}在功能上是一样;
Message Expressions: #{...}:获取国际化内容
Link URL Expressions: @{...}:定义URL;
Fragment Expressions: ~{...}:片段引用表达式
Literals(字面量)
Text literals: 'one text' , 'Another one!' ,…
Number literals: 0 , 34 , 3.0 , 12.3 ,…
Boolean literals: true , false
Null literal: null
Literal tokens: one , sometext , main ,…
Text operations:(文本操作)
String concatenation: +
Literal substitutions: |The name is ${name}|
Arithmetic operations:(数学运算)
Binary operators: + , - , * , / , %
Minus sign (unary operator): -
Boolean operations:(布尔运算)
Binary operators: and , or
Boolean negation (unary operator): ! , not
Comparisons and equality:(比较运算)
Comparators: > , < , >= , <= ( gt , lt , ge , le )
Equality operators: == , != ( eq , ne )
Conditional operators:条件运算(三元运算符)
If-then: (if) ? (then)
If-then-else: (if) ? (then) : (else)
Default: (value) ?: (defaultvalue)
Special tokens:
No-Operation: _
练习测试:
1、 我们编写一个Controller,放一些数据
@RequestMapping("/t2")
public String test2(Map<String,Object> map){
//存入数据
map.put("msg","<h1>Hello</h1>");
map.put("users", Arrays.asList("zp","zhangpeng"));
//classpath:/templates/test.html
return "text3";
}
<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>狂神说</title>
</head>
<body>
<h1>测试页面</h1>
<div th:text="${msg}"></div>
<!--不转义-->
<div th:utext="${msg}"></div>
<!--遍历数据-->
<!--th:each每次遍历都会生成当前这个标签:官网#9-->
<h4 th:each="user :${users}" th:text="${user}"></h4>
<h4>
<!--行内写法:官网#12-->
<span th:each="user:${users}">[[${user}]]</span>
</h4>
</body>
</html>
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