spring boot 开发单体应用

阳光穿透心脏的1/2处 2024-04-06 12:23 56阅读 0赞

#### 文章目录 ####

*  探究· Web开发
 *   *  静态资源处理
     *   *  静态资源映射规则·结论
         *  自定义静态资源路径
 *  Thymeleaf
 *   *  模板引擎
     *  引入Thymeleaf
     *  使用分析·thymeleaf
     *  注意事项
     *   *  表达式
 *  MVC自动配置原理【建议跳过】
 *   *  ContentNegotiatingViewResolver·内容协商视图解析器
     *  实现
 *  配置项目环境及首页
 *   *  依赖
     *   *  mybatis整合·代码·依赖
         *  其他依赖
     *  导入·实体类
     *  伪造·数据
     *  controller层
     *  注意Maven资源导出问题
     *  导入静态资源
     *  首页实现
     *  页面国际化
     *   *  准备工作
     *  配置页面国际化值
     *  设置按钮切换中英文
 *  登录+拦截器
 *   *  禁用模板缓存
     *  登录

## 探究· Web开发 ##

### 静态资源处理 ###

#### 静态资源映射规则·结论 ####

*  对于初学者来说，纠结于原理，只会让自己陷入痛苦之中。
 *  这里只给出结论，先不探究原理
 *  所以得出结论，以下四个目录存放的静态资源可以被我们识别：

"classpath:/META-INF/resources/"
    "classpath:/resources/"
    "classpath:/static/"
    "classpath:/public/"

*  可以在resources根目录下新建对应的文件夹，都可以存放我们的静态文件

#### 自定义静态资源路径 ####

*  也可以自己通过配置文件来指定一下，哪些文件夹是需要我们放静态资源文件的，在application.properties中配置；

spring.resources.static-locations=classpath:/coding/,classpath:/xxx/

***一旦自己定义了静态文件夹的路径，原来的自动配置就都会失效了！***

## Thymeleaf ##

### 模板引擎 ###

*  SpringBoot推荐你可以来使用模板引擎：
    
     *  其实jsp就是一个模板引擎，还有以用的比较多的freemarker，包括SpringBoot给我们推荐的Thymeleaf，模板引擎有非常多，但再多的模板引擎，他们的思想都是一样的,来看一下这张图：  
        ![在这里插入图片描述][244083cf3f474003b6ed86819febd873.png]
 *  模板引擎的作用
    
     *  写一个页面模板，比如：有些来自在后台封装一些动态的数据值，我们通过书写一些表达式。把这个模板和这个数据交给模板引擎，模板引擎帮我们把这表达式解析、填充到指定的位置，然后把这个数据最终生成一个完整的内容写出去，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。

### 引入Thymeleaf ###

*  [Thymeleaf 官网][Thymeleaf]
 *  [Thymeleaf 在Github 的主页][Thymeleaf _Github]
 *  [Spring官方文档][Spring]

### 使用分析·thymeleaf ###

*  首先得按照SpringBoot的自动配置原理看一下这个Thymeleaf的自动配置规则，再按照那个规则，进行使用。
 *  打开Thymeleaf的自动配置类\*\*\*【ThymeleafProperties】\*\*\*

> 诀窍：双击shift打开全局搜索，输入ThymeleafProperties，然后点开项目->定位图标，即可快速定位。  
> ![在这里插入图片描述][0b274b4d12d446c9b51808602fa19ba5.png]

@ConfigurationProperties(prefix = "spring.thymeleaf")
    public class ThymeleafProperties {
        
    
    	private static final Charset DEFAULT_ENCODING = StandardCharsets.UTF_8;
    
    	public static final String DEFAULT_PREFIX = "classpath:/templates/";
    
    	public static final String DEFAULT_SUFFIX = ".html";
    
    	/**
    	 * Whether to check that the template exists before rendering it.
    	 */
    	private boolean checkTemplate = true;
    
    	/**
    	 * Whether to check that the templates location exists.
    	 */
    	private boolean checkTemplateLocation = true;
    
    	/**
    	 * Prefix that gets prepended to view names when building a URL.
    	 */
    	private String prefix = DEFAULT_PREFIX;
    
    	/**
    	 * Suffix that gets appended to view names when building a URL.
    	 */
    	private String suffix = DEFAULT_SUFFIX;
    
    	/**
    	 * Template mode to be applied to templates. See also Thymeleaf's TemplateMode enum.
    	 */
    	private String mode = "HTML";
    
    	/**
    	 * Template files encoding.
    	 */
    	private Charset encoding = DEFAULT_ENCODING;
    
    	/**
    	 * Whether to enable template caching.
    	 */
    	private boolean cache = true;
    
    	/**
    	 * Order of the template resolver in the chain. By default, the template resolver is
    	 * first in the chain. Order start at 1 and should only be set if you have defined
    	 * additional "TemplateResolver" beans.
    	 */
    	private Integer templateResolverOrder;
    }

*  可以在其中看到默认的前缀和后缀
 *  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
 *  使用thymeleaf什么都不需要配置，只需要将他放在指定的文件夹下

### 注意事项 ###

*  使用thymeleaf要在html页面引入，命名空间

xmlns:th="http://www.thymeleaf.org"

![在这里插入图片描述][6dd0b03a275641ea9330a0f7c0d6aac2.png]

#### 表达式 ####

Simple expressions:（表达式语法）
    Variable Expressions: ${...}：获取变量值；OGNL;
    1）、获取对象的属性、调用方法
    2）、使用内置的基本对象： #18
    #ctx : the context object.
    #vars: the context variables.
    #locale : the context locale.
    #request : (only in Web Contexts) the HttpServletRequest object.
    #response : (only in Web Contexts) the HttpServletResponse object.
    #session : (only in Web Contexts) the HttpSession object.
    #servletContext : (only in Web Contexts) the ServletContext object.
    3）、内置的一些工具对象：
    #execInfo : information about the template being processed.
    #uris : methods for escaping parts of URLs/URIs
    #conversions : methods for executing the configured conversionservice (if any).
    #dates : methods for java.util.Date objects: formatting, componentextraction, etc.
    #calendars : analogous to #dates , but for java.util.Calendarobjects.
    #numbers : methods for formatting numeric objects.
    #strings : methods for String objects: contains, startsWith,prepending/appending, etc.
    #objects : methods for objects in general.
    #bools : methods for boolean evaluation.
    #arrays : methods for arrays.
    #lists : methods for lists.
    #sets : methods for sets.
    #maps : methods for maps.
    #aggregates : methods for creating aggregates on arrays orcollections.
    Selection Variable Expressions: *{...}：选择表达式：和${}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: _

## MVC自动配置原理【建议跳过】 ##

*  ***非常抱歉，由于作者的水平有限，这一部分讲解的比较模糊。***
 *  在进行项目编写前，我们还需要知道一个东西，就是SpringBoot对我们的SpringMVC还做了哪些配置，包括如何扩展，如何定制。
 *  只有把这些都搞清楚了，我们在之后使用才会更加得心应手。 途径一：源码分析，途径二：[官方文档！][Link 1]

Spring MVC Auto-configuration
    // Spring Boot为Spring MVC提供了自动配置，它可以很好地与大多数应用程序一起工作。
    Spring Boot provides auto-configuration for Spring MVC that works well with
    most applications.
    // 自动配置在Spring默认设置的基础上添加了以下功能：
    The auto-configuration adds the following features on top of Spring’s
    defaults:
    // 包含视图解析器
    Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.
    // 支持静态资源文件夹的路径，以及webjars
    Support for serving static resources, including support for WebJars
    // 自动注册了Converter：
    // 转换器，这就是我们网页提交数据到后台自动封装成为对象的东西，比如把"1"字符串自动转换为
    int类型
    // Formatter：【格式化器，比如页面给我们了一个2019-8-10，它会给我们自动格式化为Date对
    象】
    Automatic registration of Converter, GenericConverter, and Formatter beans.
    // HttpMessageConverters
    // SpringMVC用来转换Http请求和响应的的，比如我们要把一个User对象转换为JSON字符串，可以
    去看官网文档解释；
    Support for HttpMessageConverters (covered later in this document).
    // 定义错误代码生成规则的
    Automatic registration of MessageCodesResolver (covered later in this
    document).
    // 首页定制
    Static index.html support.
    // 图标定制
    Custom Favicon support (covered later in this document).
    // 初始化数据绑定器：帮我们把请求数据绑定到JavaBean中！
    Automatic use of a ConfigurableWebBindingInitializer bean (covered later in
    this document).
    /*
    如果您希望保留Spring Boot MVC功能，并且希望添加其他MVC配置（拦截器、格式化程序、视图控制
    器和其他功能），则可以添加自己
    的@configuration类，类型为webmvcconfiguer，但不添加@EnableWebMvc。如果希望提供
    RequestMappingHandlerMapping、RequestMappingHandlerAdapter或
    ExceptionHandlerExceptionResolver的自定义
    实例，则可以声明WebMVCregistrationAdapter实例来提供此类组件。
    */
    If you want to keep Spring Boot MVC features and you want to add additional
    MVC configuration
    (interceptors, formatters, view controllers, and other features), you
    can add your own
    @Configuration class of type WebMvcConfigurer but without @EnableWebMvc.
    If you wish to provide
    custom instances of RequestMappingHandlerMapping,
    RequestMappingHandlerAdapter, or
    ExceptionHandlerExceptionResolver, you can declare a
    WebMvcRegistrationsAdapter instance to provide such components.
    // 如果您想完全控制Spring MVC，可以添加自己的@Configuration，并用@EnableWebMvc进行
    注释。
    If you want to take complete control of Spring MVC, you can add your own
    @Configuration annotated with @EnableWebMvc.

### ContentNegotiatingViewResolver·内容协商视图解析器 ###

*  自动配置了ViewResolver，就是我们之前学习的SpringMVC的视图解析器；
 *  即根据方法的返回值取得视图对象（View），然后由视图对象决定如何渲染（转发，重定向）。
 *  找到 WebMvcAutoConfiguration ， 然后搜索ContentNegotiatingViewResolver

@Bean
    		@ConditionalOnBean(ViewResolver.class)
    		@ConditionalOnMissingBean(name = "viewResolver", value = ContentNegotiatingViewResolver.class)
    		public ContentNegotiatingViewResolver viewResolver(BeanFactory beanFactory) {
        
    			ContentNegotiatingViewResolver resolver = new ContentNegotiatingViewResolver();
    			resolver.setContentNegotiationManager(beanFactory.getBean(ContentNegotiationManager.class));
    			// ContentNegotiatingViewResolver uses all the other view resolvers to locate
    			// a view so it should have a high precedence
    			// ContentNegotiatingViewResolver使用所有其他视图解析器来定位视图，因此它应该具有较高的优先级
    			resolver.setOrder(Ordered.HIGHEST_PRECEDENCE);
    			return resolver;
    		}

*  我们可以点进这类看看！找到对应的解析视图的代码；  
    ![在这里插入图片描述][4cd09ac9abfc4feaa3bd32892fbd266d.png]  
    ![在这里插入图片描述][1c813a3b93ec4926b44c7be4368fa002.png]

@Override
    	@Nullable  // 注解说明：@Nullable 即参数可为null
    	public View resolveViewName(String viewName, Locale locale) throws Exception {
        
    		if (!isCache()) {
        
    			return createView(viewName, locale);
    		}
    		else {
        
    			Object cacheKey = getCacheKey(viewName, locale);
    			View view = this.viewAccessCache.get(cacheKey);
    			if (view == null) {
        
    				synchronized (this.viewCreationCache) {
        
    					view = this.viewCreationCache.get(cacheKey);
    					if (view == null) {
        
    						// Ask the subclass to create the View object.
    						view = createView(viewName, locale);
    						if (view == null && this.cacheUnresolved) {
        
    							view = UNRESOLVED_VIEW;
    						}
    						if (view != null && this.cacheFilter.filter(view, viewName, locale)) {
        
    							this.viewAccessCache.put(cacheKey, view);
    							this.viewCreationCache.put(cacheKey, view);
    						}
    					}
    				}
    			}
    			else {
        
    				if (logger.isTraceEnabled()) {
        
    					logger.trace(formatKey(cacheKey) + "served from cache");
    				}
    			}
    			return (view != UNRESOLVED_VIEW ? view : null);
    		}
    	}

*  很抱歉到这里之后，新版的内容和旧版的内容，有很大的不同，大家可以跳过这一部分的内容。不要拘泥于剖析源码。
 *  但是把最终的结论放在这里：***ContentNegotiatingViewResolver 这个视图解析器就是用来组合所有的视图解析器的***

### 实现 ###

//ViewResolver 实现了视图解析器接口的类，就可以看作视图解析器
        @Bean
        public ViewResolver myViewResolver() {
        
            return new MyViewResolver();
        }
    
        //自定义一个自己的视图解析器MyViewResolver
        public static class MyViewResolver implements ViewResolver {
        
            @Override
            public View resolveViewName(String viewName, Locale locale) throws Exception {
        
                return null;
            }
        }
        //视图跳转
    
    
        @Override
        public void addViewControllers(ViewControllerRegistry registry) {
        
            registry.addViewController("/yang").setViewName("test");
        }

## 配置项目环境及首页 ##

### 依赖 ###

#### mybatis整合·代码·依赖 ####

<dependency>
                <groupId>org.thymeleaf</groupId>
                <artifactId>thymeleaf-spring5</artifactId>
            </dependency>
            <dependency>
                <groupId>org.thymeleaf.extras</groupId>
                <artifactId>thymeleaf-extras-java8time</artifactId>
            </dependency>

#### 其他依赖 ####

<dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
    		</dependency>
    		
     
            <dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>2.2.2</version>
            </dependency>
            
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-jdbc</artifactId>
            </dependency>
           
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <scope>runtime</scope>
            </dependency>

### 导入·实体类 ###

package com.yang.pojo;
    
    /**
     * @author 缘友一世
     * date 2022/9/10-10:25
     */
    
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public class Department {
        
        private Integer id;
        private String DepartmentName;
    }

package com.yang.pojo;
    
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    import sun.util.calendar.LocalGregorianCalendar;
    
    import java.util.Date;
    
    /**
     * @author 缘友一世
     * date 2022/9/10-10:27
     */
    @Data
    @NoArgsConstructor
    
    public class Employee {
        
        private Integer id;
        private String lastName;
        private String email;
        private Integer gender;//1 男 0 女
        private Department department;
        private Date birth;
    
        public Employee(Integer id, String lastName, String email, Integer gender, Department department) {
        
            this.id = id;
            this.lastName = lastName;
            this.email = email;
            this.gender = gender;
            this.department = department;
            //默认日期实现
            this.birth = new Date();
        }
    }

### 伪造·数据 ###

*  EmployeeDao.java

package com.yang.Dao;
    
    import com.yang.pojo.Department;
    import com.yang.pojo.Employee;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Repository;
    
    import java.util.Collection;
    import java.util.HashMap;
    import java.util.Map;
    
    /**
     * @author 缘友一世
     * date 2022/9/10-10:41
     */
    @Repository
    public class EmployeeDao {
        
        //模拟数据库中的数据
        private static Map<Integer, Employee> employees;
        @Autowired
        //员工有所属的部门
        private DepartmentDao departmentDao;
        static {
        
            //创建一个员工表
            employees=new HashMap<Integer,Employee>();
    
            employees.put(1001,new Employee(1001,"小明", "1558975826@qq.com",1,new Department(101,"教学部")));
            employees.put(1002,new Employee(1002,"小李", "1568975826@qq.com",1,new Department(102,"包装部")));
            employees.put(1003,new Employee(1003,"小红", "1578975826@qq.com",0,new Department(103,"销售部")));
            employees.put(1004,new Employee(1004,"小华", "1588975826@qq.com",1,new Department(104,"人事部")));
            employees.put(1005,new Employee(1005,"小王", "1598975826@qq.com",1,new Department(105,"主管部")));
            employees.put(1006,new Employee(1006,"小张", "1518975826@qq.com",0,new Department(106,"生产部")));
        }
        //主键自增
        private static Integer initId=1007;
        //增加一个员工
        public void add(Employee employee) {
        
            if(employee.getId()==null) {
        
                employee.setId(initId++);
            }
            employee.setDepartment(departmentDao.getDepartmentById(employee.getDepartment().getId()));
    
            employees.put(employee.getId(),employee);
        }
        //查询全部员工信息
        public Collection<Employee> getAll() {
        
            return employees.values();
        }
        //通过id查询员工
        public Employee getEmployeeById(Integer id) {
        
            return employees.get(id);
        }
        //删除员工通过id
        public void delete(Integer id) {
        
            employees.remove(id);
        }
    }

*  DepartmentDao.java

package com.yang.Dao;
    
    import com.yang.pojo.Department;
    import org.springframework.stereotype.Repository;
    
    import java.util.Collection;
    import java.util.HashMap;
    import java.util.Map;
    
    /**
     * @author 缘友一世
     * date 2022/9/10-10:32
     */
    @Repository
    public class DepartmentDao {
        
        //模拟数据库中的数据
        private static Map<Integer, Department> departments=null;
        static {
        
            departments=new HashMap<Integer,Department>();//创建一个部门表
            departments.put(101,new Department(101,"教学部"));
            departments.put(102,new Department(102,"包装部"));
            departments.put(103,new Department(103,"销售部"));
            departments.put(104,new Department(104,"人事部"));
            departments.put(105,new Department(105,"主管部"));
            departments.put(106,new Department(106,"生产部"));
        }
        //获得所有部门信息
        public static Collection<Department> getDepartments() {
        
            return departments.values();
        }
        //通过id获得部门
        public Department getDepartmentById(Integer id) {
        
            return departments.get(id);
        }
    }

### controller层 ###

*  EmployeeController

package com.yang.config;
    
    import com.yang.Dao.DepartmentDao;
    import com.yang.Dao.EmployeeDao;
    import com.yang.pojo.Department;
    import com.yang.pojo.Employee;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Controller;
    import org.springframework.ui.Model;
    import org.springframework.web.bind.annotation.*;
    
    import javax.jws.WebParam;
    import java.util.Collection;
    
    /**
     * @author 缘友一世
     * date 2022/9/10-20:46
     */
    @Controller
    public class EmployeeController {
        
        @Autowired
        EmployeeDao employeeDao;
        @RequestMapping("/emps")
        public String list(Model model) {
        
            Collection<Employee> employees = employeeDao.getAll();
            model.addAttribute("emps",employees);
            return "emp/list";
        }
        @GetMapping("/emp")
        public String toAddPage(Model model) {
        
            //查询出所有部门信息
            Collection<Department> departments = DepartmentDao.getDepartments();
            model.addAttribute("departments",departments);
            return "emp/add";
        }
        @PostMapping("/emp")
        public String addEmp(Employee employee) {
        
            employeeDao.add(employee);
            return "redirect:/emps";
        }
        @GetMapping("/emp/{id}")
        public String toUpdate(@PathVariable("id")Integer id, Model model) {
        
            //查出原来的数据
            Employee employee = employeeDao.getEmployeeById(id);
            model.addAttribute("emp",employee);
            Collection<Department> departments = DepartmentDao.getDepartments();
            model.addAttribute("departments",departments);
            return "emp/update";
        }
        @PostMapping("/updateEmp")
        public String updateEmp(Employee employee) {
        
            employeeDao.add(employee);
            return "redirect:/emps";
        }
        @GetMapping("/delemp/{id}")
        public String deleteEmp(@PathVariable("id") int id) {
        
            employeeDao.delete(id);
            return "redirect:/emps";
        }
    }

### 注意Maven资源导出问题 ###

*  build标签内

### 导入静态资源 ###

1.  css，js等放在static文件夹下
2.  html 放在 templates文件夹下

*  结构图  
    ![在这里插入图片描述][53ae7f0d74084f928b949761a31c2632.png]

### 首页实现 ###

*  自己编写MVC的扩展配置

@Override
        public void addViewControllers(ViewControllerRegistry registry) {
        
            registry.addViewController("/").setViewName("index");
            registry.addViewController("/index.html").setViewName("index");
            registry.addViewController("/main.html").setViewName("dashboard");
        }

*  解决了首页问题，我们还需要解决一个资源导入的问题；
 *  为了保证资源导入稳定，我们建议在所有资源导入时候使用 th:去替换原有的资源路径！这也是模板规范

### 页面国际化 ###

#### 准备工作 ####

*  先在IDEA中统一设置properties的编码问题  
    ![在这里插入图片描述][027c60bd3911421bbcd348279ecafa74.png]
 *  配置文件编写
    
     *  在resources资源文件下新建一个i18n目录，存放国际化配置文件
     *  建立一个login.properties文件，还有一个login\_zh\_CN.properties；发现IDEA自动识别了我们要做  
        国际化操作；文件夹变了！  
        ![在这里插入图片描述][fddb4aeaa6f84ebf874ac888533ee2a0.png]  
        ![在这里插入图片描述][2110675855d44174a991bd3a8dc33c97.png]
     *  接下来，我们就来编写配置  
        ![在这里插入图片描述][cd710d2d747e42f6b70ed9cf6e74f3c2.png]
     *  这个视图我们点击 + 号就可以直接添加属性了；我们新建一个login.tip，可以看到边上有三个文件框可以输入  
        ![在这里插入图片描述][a59aa100dad5423995aae3a090bf7075.png]  
        ![在这里插入图片描述][f7a9223d7eb64473af2f5a1ea2150478.png]
     *  然后去查看我们的配置文件
        
         *  login.properties ： 默认
    
        login.username=用户名
        login.btn=登录
        login.password=密码
        login.remember=记住我
        login.tip=请登录
    
        - 英文
    
        login.username=username
        login.btn=Sign in
        login.password=Password
        login.remember=Remember me
        login.tip=Please sign in
    
        - 中文
    
        login.username=用户名
        login.btn=登录
        login.password=密码
        login.remember=记住我
        login.tip=请登录

### 配置页面国际化值 ###

*  去页面获取国际化的值，查看Thymeleaf的文档，找到message取值操作为： \#\{…\}

<!DOCTYPE html>
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
    	<head>
    		<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    		<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    		<meta name="description" content="">
    		<meta name="author" content="">
    		<title>Sign in Template for Bootstrap</title>
    		
    		<link th:href="@{/css/bootstrap.min.css}" rel="stylesheet">
    		
    		<link th:href="@{/css/signin.css}" rel="stylesheet">
    		<style>
    			#tip {
        
    				color: red;
    			}
    		</style>
    	</head>
    
    	<body class="text-center">
    		<form class="form-signin" th:action="@{/user/login}">
    			<img class="mb-4" th:src="@{/img/bootstrap-solid.svg}" alt="" width="72" height="72">
    			<h1 class="h3 mb-3 font-weight-normal" th:text="#{login.tip}">Please sign in</h1>
    
    			
    			<p id="tip" th:text="${msg}" th:if="${not #strings.isEmpty(msg)}"></p>
    
    			<label class="sr-only" >Username</label>
    			<input type="text" class="form-control" name="username" th:placeholder="#{login.username}"  required="" autofocus="">
    			<label class="sr-only" name="password" >Password</label>
    			<input type="password" class="form-control" name="password" th:placeholder="#{login.password}" required="">
    			<div class="checkbox mb-3">
    				<label>
              <input type="checkbox" value="remember-me">[[#{
        login.remember}]]
            </label>
    			</div>
    			<button class="btn btn-lg btn-primary btn-block" type="submit" >[[#{
        login.btn}]]</button>
    			<p class="mt-5 mb-3 text-muted">© 2017-2018</p>
    			<a class="btn btn-sm" th:href="@{/index.html(l='zh_CN')}">中文</a>
    			<a class="btn btn-sm" th:href="@{/index.html(l='en_US')}">English</a>
    		</form>
    
    	</body>
    
    </html>

![在这里插入图片描述][9db8783283a544d38544609f861b619d.png]

### 设置按钮切换中英文 ###

*  配置国际化解析
    
     *  在Spring中有一个国际化的Locale （区域信息对象）；里面有一个叫做LocaleResolver （获取区域信息对象）的解析器！
     *  我们去我们webmvc自动配置文件，寻找一下！看到SpringBoot默认配置：

@Bean
    @ConditionalOnMissingBean
    @ConditionalOnProperty(prefix = "spring.mvc", name = "locale")
    public LocaleResolver localeResolver() {
        
    	// 容器中没有就自己配，有的话就用用户配置的
    	if (this.mvcProperties.getLocaleResolver() ==
    	WebMvcProperties.LocaleResolver.FIXED) {
        
    		return new FixedLocaleResolver(this.mvcProperties.getLocale());
    	}
    	// 接收头国际化分解
    	AcceptHeaderLocaleResolver localeResolver = new
    	AcceptHeaderLocaleResolver();
    	localeResolver.setDefaultLocale(this.mvcProperties.getLocale());
    	return localeResolver;
    }

*  AcceptHeaderLocaleResolver 这个类中有一个方法

public Locale resolveLocale(HttpServletRequest request) {
        
    	Locale defaultLocale = this.getDefaultLocale();
    	// 默认的就是根据请求头带来的区域信息获取Locale进行国际化
    	if (defaultLocale != null && request.getHeader("Accept-Language") ==
    null) {
        
    	return defaultLocale;
    } else {
        
    	Locale requestLocale = request.getLocale();
    	List<Locale> supportedLocales = this.getSupportedLocales();
    	if (!supportedLocales.isEmpty() && !supportedLocales.contains(requestLocale)) {
        
    		Locale supportedLocale = this.findSupportedLocale(request,supportedLocales);
    		if (supportedLocale != null) {
        
    			return supportedLocale;
    		} else {
        
    			return defaultLocale != null ? defaultLocale :requestLocale;
    			}
    		} else {
        
    			return requestLocale;
    		}
    	}
    }

*  如果想点击链接让我们的国际化资源生效，就需要让我们自己的Locale生效！
 *  我们去自己写一个自己的LocaleResolver，可以在链接上携带区域信息！
 *  修改一下前端页面的跳转连接：

<a class="btn btn-sm" th:href="@{/index.html(l='zh_CN')}">中文</a>
    <a class="btn btn-sm" th:href="@{/index.html(l='en_US')}">English</a>

*  处理的组件类

package com.yang.config;
    
    import org.springframework.util.StringUtils;
    import org.springframework.web.servlet.LocaleResolver;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.util.Locale;
    
    /**
     * @author 缘友一世
     * date 2022/9/10-13:15
     */
    public class MyLocalResolver implements LocaleResolver {
        
        @Override
        public Locale resolveLocale(HttpServletRequest request) {
        
            //获取请求中的语言参数
            String language = request.getParameter("l");
            Locale locale = Locale.getDefault(); // 如果没有获取到就使用系统默认的
            //如果请求链接不为空
            if (!StringUtils.isEmpty(language)){
        
                //分割请求参数
                String[] split = language.split("_");
                //国家，地区
                locale = new Locale(split[0],split[1]);
            }
            return locale;
        }
    
        @Override
        public void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) {
        
    
        }
    
    }

*  为了让我们的区域化信息能够生效，我们需要再配置一下这个组件！在我们自己的MvcConofig下添加  
    bean；

@Bean
        public LocaleResolver localeResolver(){
        
            return new MyLocalResolver();
        }

## 登录+拦截器 ##

### 禁用模板缓存 ###

> 说明：页面存在缓存，所以我们需要禁用模板引擎的缓存

spring:
      thymeleaf:
        cache: false #关闭模板引擎的缓存

> 模板引擎修改后，想要实时生效！页面修改完毕后，IDEA小技巧 ： Ctrl + F9 重新编译！即可生效！

### 登录 ###

1.  把登录页面的表单提交地址写一个controller

<form class="form-signin" th:action="@{/user/login}" method="post">
    		//这里面的所有表单标签都需要加上一个name属性
    </form>

1.  编写对应的controller

package com.yang.config;
    
    import org.springframework.stereotype.Controller;
    import org.springframework.ui.Model;
    import org.springframework.util.ObjectUtils;
    import org.springframework.util.StringUtils;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestParam;
    import org.springframework.web.bind.annotation.ResponseBody;
    
    import javax.servlet.http.HttpSession;
    
    /**
     * @author 缘友一世
     * date 2022/9/10-15:18
     */
    @Controller
    public class LoginController {
        
        @RequestMapping("/user/login")
        public String login(
                @RequestParam("username") String username,
                @RequestParam("password") String password,
                Model model, HttpSession httpSession) {
        
            //业务逻辑
            if(!ObjectUtils.isEmpty(username) && "5201314".equals(password)) {
        
                httpSession.setAttribute("loginUser",username);
                return "redirect:/main.html";
            }else {
        
                //告诉用户，登陆失败
                model.addAttribute("msg","用户名或者密码错误！");
                return "index";
            }
        }
        @RequestMapping("/user/logout")
        public String logout(HttpSession session) {
        
            //session 的作用域是在一个会话期间，多个用户访问服务器，就会有多个session
            //session.invalidate()，它实际上调用的是session对象中的destroy方法，也就是说你下次要再使用session，得再重新创建
            session.invalidate();
            return "direct:/index.html";
        }
    }

1.  登录拦截器

*  我们可以直接登录到后台主页，不用登录也可以实现！怎么处理这个问题呢？我们可以使用拦截器机制，实现登录检查！
    
     *  先自定义一个拦截器：
    
        public class LoginHandlerInterceptor implements HandlerInterceptor {
              
            @Override
            public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
              
                //登录之后，应该有用户的session
                Object loginUser = request.getSession().getAttribute("loginUser");
                if(loginUser==null) {
              
                    request.setAttribute("msg","没有权限，请先登录");
                    request.getRequestDispatcher("/index.html").forward(request,response);
                    return false;
                }else {
              
                    return true;
                }
            }
        }
    
     *  然后将拦截器注册到我们的SpringMVC配置类当中
    
        @Override
        public void addInterceptors(InterceptorRegistry registry) {
              
            registry.addInterceptor(new LoginHandlerInterceptor()).
                    addPathPatterns("/**").excludePathPatterns("/index.html","/","/user/login","/js/**","/css/**","/img/**");
        }
    
     *  然后在后台主页，获取用户登录的信息

<a class="navbar-brand col-sm-3 col-md-2 mr-0" href="http://getbootstrap.com/docs/4.0/examples/dashboard/#">[[${session.loginUser}]]</a>

*  结束了  
    ![在这里插入图片描述][60bf1b4c31d94061ad9e665520982b4b.jpeg_pic_center]

[244083cf3f474003b6ed86819febd873.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/3357b66d59ef409d99620be590209aaf.png
[Thymeleaf]: https://www.thymeleaf.org/
[Thymeleaf _Github]: https://github.com/thymeleaf/thymeleaf
[Spring]: https://docs.spring.io/spring-boot/docs/2.2.5.RELEASE/reference/htmlsingle/#using-boot-starter
[0b274b4d12d446c9b51808602fa19ba5.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/ab790444135645629e7d56d5bf874140.png
[6dd0b03a275641ea9330a0f7c0d6aac2.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/71e00738eaf444bebccff63400b33dc9.png
[Link 1]: https://docs.spring.io/spring-boot/docs/2.2.5.RELEASE/reference/htmlsingle/#boot-feature%20s-spring-mvc-auto-configuration
[4cd09ac9abfc4feaa3bd32892fbd266d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/bc41ed32a11b4761891df7737f8a8379.png
[1c813a3b93ec4926b44c7be4368fa002.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/85ed77e51bad43198d75d9298041b4d8.png
[53ae7f0d74084f928b949761a31c2632.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/fa943afed063492a8c6376ad6a63c939.png
[027c60bd3911421bbcd348279ecafa74.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/6e8665eefa36413d98b874712d4e4ad5.png
[fddb4aeaa6f84ebf874ac888533ee2a0.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/08c23364d17241499d1fff9e1a664436.png
[2110675855d44174a991bd3a8dc33c97.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/58b37b3216824304a637d111b310ff67.png
[cd710d2d747e42f6b70ed9cf6e74f3c2.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/2ef59a176deb4111b88a72c2e5d6ab12.png
[a59aa100dad5423995aae3a090bf7075.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/7bb96db248324d0aa330e471d1e5ccaa.png
[f7a9223d7eb64473af2f5a1ea2150478.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/2d8dc04ff79e4c74b000194429197382.png
[9db8783283a544d38544609f861b619d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/a964612031d844699a1af90299abc010.png
[60bf1b4c31d94061ad9e665520982b4b.jpeg_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/06/275c22d1b6184a87a6999bfb7b246332.jpeg