SpringBoot--Web篇<一>

1.使用SpringBoot开发web步骤

1）创建SpringBoot应用，选中我们需要的模块；
2）SpringBoot已经默认将这些场景配置好了，只需要在配置文件中指定少量配置就可以运行起来
3）自己编写业务代码；

2.SpringBoot对静态资源的映射规则

2.1 所有 /webjars/** ，都去 classpath:/META-INF/resources/webjars/ 找资源；
webjars：以jar包的方式引入静态资源；

2.2 "/**" 访问当前项目的任何资源，都去（静态资源的文件夹）找映射

"classpath:/META‐INF/resources/",
"classpath:/resources/",
"classpath:/static/",
"classpath:/public/"
"/"：当前项目的根路径

localhost:8080/cyy === 去静态资源文件夹里面找cyy

2.3 欢迎页；静态资源文件夹下的所有index.html页面；被"/**"映射；
localhost:8080/ 找index页面

2.4 所有的 **/favicon.ico 都是在静态资源文件下找；

3.模板引擎

3.1 常见的模板引擎有：JSP、Velocity、Freemarker、Thymeleaf等，SpringBoot中推荐使用Thymeleaf

3.2 引入Thymeleaf


        
            org.springframework.boot
            spring-boot-starter-thymeleaf
        
        


        3.0.9.RELEASE
        
        2.2.2

3.3 Thymeleaf的使用与语法
先看看ThymeleafProperties类中的方法

@ConfigurationProperties(
    prefix = "spring.thymeleaf"
)
public class ThymeleafProperties {
    private static final Charset DEFAULT_ENCODING;
    public static final String DEFAULT_PREFIX = "classpath:/templates/";
    public static final String DEFAULT_SUFFIX = ".html";
    private boolean checkTemplate = true;
    private boolean checkTemplateLocation = true;
    private String prefix = "classpath:/templates/";
    private String suffix = ".html";
    private String mode = "HTML";
    private Charset encoding;
    private boolean cache;
    private Integer templateResolverOrder;
    private String[] viewNames;
    private String[] excludedViewNames;
    private boolean enableSpringElCompiler;
    private boolean enabled;
    private final ThymeleafProperties.Servlet servlet;
    private final ThymeleafProperties.Reactive reactive;

只要我们把HTML页面放在classpath:/templates/，Thymeleaf就能自动渲染；

踩的坑：
由于我Controller中注解给的是@RestController，模板引擎不会渲染，只会返回JSON格式，后改为@Controller，才能正常渲染。

使用：

3.3.1 导入thymeleaf的名称空间，引入后页面就会提示thymeleaf语法

3.3.2 使用thymeleaf语法




   
   Success


成功！
 
 这是显示欢迎信息

3.3.3 语法规则

1） th:text; 改变当前元素里面的文本内容；
th:任意的html属性，来替换原生属性的值
2）表达式

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：
     #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.

例:${session.foo}
        3）内置的一些工具对象：
#execInfo : information about the template being processed.
#messages : methods for obtaining externalized messages inside variables expressions,in the
same way as they would be obtained using #{…} syntax.
#uris : methods for escaping parts of URLs/URIs
#conversions : methods for executing the configured conversion service (if any).
#dates : methods for java.util.Date objects: formatting, component extraction,etc.
#calendars : analogous to #dates ,but for java.util.Calendar objects.
#numbers:methods for formatting numeric objects.
#strings:methods for String objects: contains,startsWith,prepending/appending,etc.
#objects:methods for objectsin general.
#bools: methods for boolean evaluation.
#arrays:methods for arrays.
#lists:methods for lists.
#sets:methods for sets.
#maps:methods for maps.
#aggregates : methods for creating aggregates on arrays or collections.
#ids:methods for dealing with id attributes that might be repeated (for example,as a
result of an iteration).
    Selection Variable Expressions: *{...}：选择表达式：和${}在功能上是一样；
     补充：配合 th:object="${session.user}： 
    
    Name:Sebastian.
    Surname: Pepper.
    Nationality:Saturn.
    

    Message Expressions: #{...}：获取国际化内容
    Link URL Expressions: @{...}：定义URL；
     @{/order/process(execId=${execId},execType='FAST')}
    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: _

3）实战

package com.cyy.springboot_web.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;

import java.util.Arrays;
import java.util.Map;

/**
 * @Author cyy
 * @Date 2018/8/10 17:54
 * @Version 1.0
 * @Blog http://pccwcyy.club/wordpress/
 **/
@Controller
public class HelloController {

    @GetMapping("/hello")
    public String hello(){
        return "hello";
    }

    @GetMapping("/success")
    public String success(Map map) {
        map.put("hello","你好");
        map.put("users", Arrays.asList("ccc","ddd","eee"));
        //模板引擎会自动搜索页面 classpath:/templates/success.html
        return "success";
    }

}




    
    Success


登录成功！
这里是不加载引擎模板时候的显示内容









    [[${user}]]

演示Demo