java篇-(java使用内嵌Tomcat开发javaWeb项目-初级篇)

Bertha 。 2023-01-17 10:40 216阅读 0赞

### java使用内嵌tomcat开发web项目 ###

*  写在前面
 *  初始化项目
 *   *  使用idea构建kotlin项目
     *  pom.xml文件如下
 *  启动tomcat服务
 *   *  使用java语言
     *  使用kotlin语言
 *  添加过滤器
 *   *  使用java语言
     *  使用kotlin语言
 *  自定义sessionId生成器
 *   *  使用java语言
     *  使用kotlin语言
 *  添加模板引擎的支持
 *   *  添加thymeleaf支持
     *   *  添加pom依赖
         *  添加thymeleaf支持的Servlet
         *   *  使用java语言
             *  使用Kotlin语言
     *  使用freemarker
     *   *  添加pom依赖
         *  添加FreemarkerServlet，并在启动类里面使用
         *   *  使用java语言
             *  使用kotlin语言
 *  完整代码
 *   *  java语言
     *  kotlin语言

# 写在前面 #

`本项目使用开发软件为idea，版本控制使用maven，同时支持kotlin`

# 初始化项目 #

## 使用idea构建kotlin项目 ##

`这里点击file，选择new project，然后选择kotlin，输入右侧一些信息之后，选择next`  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70]  
`然后选择与上面jdk一样的版本，点击finish`  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 1]

## pom.xml文件如下 ##

`这里添加tomcat-embed-core依赖，同时添加java编译插件，让java文件拥有11的新特性`

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0" 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>
    
        <artifactId>embed-tomcat-example</artifactId>
        <groupId>com.lhstack</groupId>
        <version>0.0.1</version>
        <packaging>jar</packaging>
    
        <name>embed-tomcat-example</name>
    
        <properties>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <kotlin.code.style>official</kotlin.code.style>
            <kotlin.compiler.jvmTarget>11</kotlin.compiler.jvmTarget>
            <tomcat.embed.version>9.0.31</tomcat.embed.version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-test-junit</artifactId>
                <version>1.4.10</version>
                <scope>test</scope>
            </dependency>
    
            <dependency>
                <groupId>org.apache.tomcat.embed</groupId>
                <artifactId>tomcat-embed-core</artifactId>
                <version>${tomcat.embed.version}</version>
            </dependency>
    
            <dependency>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-stdlib-jdk8</artifactId>
                <version>1.4.10</version>
            </dependency>
        </dependencies>
    
        <repositories>
            <repository>
                <id>mavenCentral</id>
                <url>https://repo1.maven.org/maven2/</url>
            </repository>
        </repositories>
    
        <build>
            <sourceDirectory>src/main/kotlin</sourceDirectory>
            <testSourceDirectory>src/test/kotlin</testSourceDirectory>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.8.1</version>
                    <configuration>
                        <target>11</target>
                        <source>11</source>
                        <encoding>UTF-8</encoding>
                    </configuration>
                </plugin>
                <plugin>
                    <groupId>org.jetbrains.kotlin</groupId>
                    <artifactId>kotlin-maven-plugin</artifactId>
                    <version>1.4.10</version>
                    <executions>
                        <execution>
                            <id>compile</id>
                            <phase>compile</phase>
                            <goals>
                                <goal>compile</goal>
                            </goals>
                        </execution>
                        <execution>
                            <id>test-compile</id>
                            <phase>test-compile</phase>
                            <goals>
                                <goal>test-compile</goal>
                            </goals>
                        </execution>
                    </executions>
                </plugin>
                <plugin>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.22.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-failsafe-plugin</artifactId>
                    <version>2.22.2</version>
                </plugin>
            </plugins>
        </build>
    </project>

# 启动tomcat服务 #

## 使用java语言 ##

package com.lhstack.embed;
    
    import org.apache.catalina.Wrapper;
    import org.apache.catalina.startup.Tomcat;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    /** * @author lhstack */
    public class EmbedTomcatApplication { 
        public static void main(String[] args) throws Exception { 
            //tomcat监听端口
            int port = 8080;
    // //tomcat的baseDir，如果是内嵌的，不需要启动war包项目，可以不需要设置此参数,这里就说明一下，不做配置
    // String baseDir = System.getProperty("user.dir") + "/tomcat";
    // //这里tomcat需要读取baseDir下面的webapps目录，并不会自动创建，所以需要单独处理一下，如果不需要启动war包项目，可以不做配置
    // String webapps = baseDir + "/webapps";
    // //创建目录
    // File file = new File(webapps);
    // if(!file.exists()){ 
    // file.mkdirs();
    // }
            Tomcat tomcat = new Tomcat();
            //tomcat.setBaseDir();
    
            tomcat.setPort(port);
            //需要设置一下端口，不然无法访问
            tomcat.getConnector().setPort(port);
    
            //创建一个context
            tomcat.addContext("/", Thread.currentThread().getContextClassLoader().getResource("").getFile());
    
            //创建servlet，指向上面创建的context,通过contextPath判断
            Wrapper servlet = tomcat.addServlet("/", "HelloServlet", new HttpServlet() { 
                @Override
                protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
                    resp.getOutputStream().print("hello world");
                }
            });
            //添加映射
            servlet.addMapping("/");
    
            //启动tomcat
            tomcat.start();
    
        }
    }

通过浏览器访问 localhost:8080  
![在这里插入图片描述][20210428215735568.png]

## 使用kotlin语言 ##

package com.lhstack.embed
    
    import org.apache.catalina.startup.Tomcat
    import javax.servlet.http.HttpServlet
    import javax.servlet.http.HttpServletRequest
    import javax.servlet.http.HttpServletResponse
    
    fun main() { 
        val port:Int = 8080
        val tomcat:Tomcat = Tomcat()
        tomcat.setPort(port)
        tomcat.connector.port = port
        tomcat.addContext("/",Thread.currentThread().contextClassLoader.getResource("")!!.path)
        val servlet = tomcat.addServlet("/", "HelloServlet", object : HttpServlet() { 
            override fun doGet(req: HttpServletRequest?, resp: HttpServletResponse?) { 
                resp!!.outputStream.print("hello world")
            }
        })
        servlet.addMapping("/")
        tomcat.start()
    }

启动后访问 localhost:8080  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 2]

# 添加过滤器 #

## 使用java语言 ##

...
    		...
            //添加映射
            servlet.addMapping("/");
    
            String encoding = "UTF-8";
    
            //定义filter
            FilterDef filterDef = new FilterDef();
            filterDef.setFilterName("CharacterEncodingFilter");
            filterDef.setFilter((req, res, chain) -> { 
                if(req instanceof HttpServletRequest){ 
                    System.out.println("setting request character encoding");
                    req.setCharacterEncoding(encoding);
                }
                if(res instanceof HttpServletResponse){ 
                    System.out.println("setting response character encoding");
                    res.setCharacterEncoding(encoding);
                }
                chain.doFilter(req,res);
            });
    
            //定义filter映射
            FilterMap filterMap = new FilterMap();
            filterMap.setFilterName("CharacterEncodingFilter");
            filterMap.addURLPattern("/*");
    
            //添加filter
            context.addFilterDef(filterDef);
            context.addFilterMap(filterMap);
    
            //启动tomcat
            tomcat.start();
    
        }
    }

启动应用，查看浏览器和控制台  
![在这里插入图片描述][20210428221220725.png]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 3]

## 使用kotlin语言 ##

...
    	...
        val encoding = "UTF-8"
        val filterDef = FilterDef()
        filterDef.filterName = "CharacterFilterEncoding"
        filterDef.filter = Filter {  req, res, chain ->
            if(req is HttpServletRequest){ 
                println("setting request character encoding $encoding")
                req.characterEncoding = encoding
            }
            if(res is HttpServletResponse){ 
                println("setting response character encoding $encoding")
                res.characterEncoding = encoding
            }
            chain.doFilter(req,res)
        }
    
        val filterMap = FilterMap()
    
        filterMap.addURLPattern("/*")
        filterMap.filterName = "CharacterFilterEncoding"
    
        context.addFilterDef(filterDef)
        context.addFilterMap(filterMap)
    
        tomcat.start()
    }

启动应用，查看浏览器和控制台  
![在这里插入图片描述][20210428221734514.png]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 4]

# 自定义sessionId生成器 #

## 使用java语言 ##

...
    		...
            //创建一个context
            Context context = tomcat.addContext("/", Thread.currentThread().getContextClassLoader().getResource("").getFile());
    
            //添加context管理器 TODO
            StandardManager standardManager = new StandardManager();
            standardManager.setSessionIdGenerator(new SessionIdGeneratorBase() { 
                @Override
                public String generateSessionId(String route) { 
                    return "lhstack-uuid->" + route + "->" + UUID.randomUUID().toString().replaceAll("-","");
                }
            });
            context.setManager(standardManager);
            
            ...
            ...
    
            //启动tomcat
            tomcat.start();
    
        }
    }

启动项目,通过浏览器查看，session id  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 5]

## 使用kotlin语言 ##

...
    	...
        val context = tomcat.addContext("/", Thread.currentThread().contextClassLoader.getResource("")!!.path)
        ...
        ...
        //添加context关联器
        context.manager = StandardManager()
    
        context.manager.sessionIdGenerator = object:SessionIdGeneratorBase(){ 
            override fun generateSessionId(route: String?): String { 
                return "lhstack->uuid->${UUID.randomUUID().toString().replace("-","")}"
            }
        }
        ...
        ...
        tomcat.start()
    }

# 添加模板引擎的支持 #

## 添加thymeleaf支持 ##

### 添加pom依赖 ###

`在pom.xml添加如下依赖`

<dependency>
       <groupId>org.thymeleaf</groupId>
       <artifactId>thymeleaf</artifactId>
       <version>${thymeleaf.version}</version>
    </dependency>

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 7]

### 添加thymeleaf支持的Servlet ###

#### 使用java语言 ####

...
    		//这里修改之前第一个创建的servlet，选择转发的方式
    		//创建一个context
            Context context = tomcat.addContext("/", Thread.currentThread().getContextClassLoader().getResource("").getFile());
    
            //创建servlet，指向上面创建的context,通过contextPath判断
            Wrapper servlet = tomcat.addServlet("/", "HelloServlet", new HttpServlet() { 
                @Override
                protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
                    //修改之前的输出，这里为了测试模板引擎的功能，所以选择转发
                    req.getRequestDispatcher("index.html").forward(req,resp);
                }
            });
            //添加映射
            servlet.addMapping("/");
            ...

添加创建thymeleaf servlet的静态方法

public static void addThymeleafServlet(Context context,Tomcat tomcat){ 
    		//这里context上下文，thymeleaf会去加载context的docBase目录下面的资源，所以之前我在创建context时，添加了当前classpath路径作为docBase路径
            ServletContext servletContext = context.getServletContext();
            ServletContextTemplateResolver contextTemplateResolver = new ServletContextTemplateResolver(servletContext);
            TemplateEngine templateEngine = new TemplateEngine();
            templateEngine.addTemplateResolver(contextTemplateResolver);
            Tomcat.addServlet(context, "ThymeleafServlet", new HttpServlet() { 
                @Override
                protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
                    DispatcherType dispatcherType = req.getDispatcherType();
                    resp.setContentType("text/html;charset=utf-8");
                    try{ 
                        String html = null;
                        if(dispatcherType == DispatcherType.FORWARD){ 
                            //如果是forward，就转发到受保护的template目录下面
                            html = templateEngine.process("/template" + req.getRequestURI(),new WebContext(req,resp,servletContext));
                        }else if(dispatcherType == DispatcherType.REQUEST){ 
                            //如果是普通请求，就映射static目录
                            html = templateEngine.process("/static" + req.getRequestURI(),new WebContext(req,resp,servletContext));
                        }
                        resp.getOutputStream().print(html);
                    }catch (Exception e){ 
                        resp.getOutputStream().print("404 not found");
                    }
                }
            }).addMapping("*.html");
        }

调用添加thymeleafServlet的方法

...
    		//添加filter
            context.addFilterDef(filterDef);
            context.addFilterMap(filterMap);
    		//这里调用添加thymeleafServlet的方法
            addThymeleafServlet(context,tomcat);
    
            //启动tomcat
            tomcat.start();

在对应目录添加html文件  
resources/static  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 8]  
resources/template  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 9]

通过浏览器测试  
访问静态路径  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 10]  
访问根路径，通过HelloServlet进行转发  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 11]

#### 使用Kotlin语言 ####

...
    	val context = tomcat.addContext("/", Thread.currentThread().contextClassLoader.getResource("")!!.path)
        val servlet = tomcat.addServlet("/", "HelloServlet", object : HttpServlet() { 
            override fun doGet(req: HttpServletRequest?, resp: HttpServletResponse?) { 
                //修改之前的输出，这里为了测试模板引擎的功能，所以选择转发
                req!!.getRequestDispatcher("index.html").forward(req,resp)
            }
        })
        ...

添加addThymeleafServlet函数

fun addThymeleafServlet(context: Context){ 
        val servletContextTemplateResolver = ServletContextTemplateResolver(context.servletContext)
        val templateEngine = TemplateEngine()
        templateEngine.addTemplateResolver(servletContextTemplateResolver)
        Tomcat.addServlet(context,"ThymeleafServlet",object:HttpServlet(){ 
            override fun doGet(req: HttpServletRequest?, resp: HttpServletResponse?) { 
                val dispatcherType = req!!.dispatcherType
                resp!!.contentType = "text/html;charset=utf-8"
                try { 
                    var html: String? = null
                    if (dispatcherType == DispatcherType.FORWARD) { 
                        //如果是forward，就转发到受保护的template目录下面
                        html = templateEngine.process("/template" + req.requestURI, WebContext(req, resp, servletContext))
                    } else if (dispatcherType == DispatcherType.REQUEST) { 
                        //如果是普通请求，就映射static目录
                        html = templateEngine.process("/static" + req.requestURI, WebContext(req, resp, servletContext))
                    }
                    resp.outputStream.print(html)
                } catch (e: Exception) { 
                    resp.outputStream.print("404 not found")
                }
            }
        }).addMapping("*.html")
        
    }

调用添加thymeleafServlet的函数

...
      	context.addFilterDef(filterDef)
        context.addFilterMap(filterMap)
        
        addThymeleafServlet(context)
    
        tomcat.start()
        ...

通过浏览器测试  
访问静态路径  
![在这里插入图片描述][20210429200508146.png]  
访问根路径，通过HelloServlet进行转发  
![在这里插入图片描述][20210429200524419.png]

## 使用freemarker ##

### 添加pom依赖 ###

在pom.xml里面添加freemarker依赖  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 12]

<dependency>
       <groupId>org.freemarker</groupId>
       <artifactId>freemarker</artifactId>
       <version>${freemarker.version}</version>
    </dependency>

### 添加FreemarkerServlet，并在启动类里面使用 ###

#### 使用java语言 ####

1.创建用于渲染freemarker模板的servlet  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 13]

package com.lhstack.embed.servlet;
    
    import freemarker.template.Configuration;
    import freemarker.template.Template;
    import freemarker.template.TemplateNotFoundException;
    
    import javax.servlet.ServletConfig;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.util.HashMap;
    import java.util.Locale;
    import java.util.Map;
    
    /** * @author lhstack */
    public class FreemarkerServlet extends HttpServlet { 
    
        private Configuration configuration = null;
    
        @Override
        public void init(ServletConfig config) throws ServletException { 
            configuration = new Configuration(Configuration.VERSION_2_3_31);
            configuration.setClassLoaderForTemplateLoading(config.getServletContext().getClassLoader(),"");
            configuration.setEncoding(Locale.CHINA,"UTF-8");
            configuration.setDefaultEncoding("UTF-8");
        }
    
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            doRender(req,resp);
        }
    
        /** * 统一渲染方法 * @param req * @param resp */
        private void doRender(HttpServletRequest req, HttpServletResponse resp) throws IOException { 
            //创建用于模板引擎中使用的变量
            Map<String,Object> model = new HashMap<>(4);
            model.put("Request",req);
            model.put("Response",resp);
            model.put("Session",req.getSession());
            model.put("Context",req.getServletContext());
            resp.setContentType("text/html;charset=utf-8");
            try{ 
                Template template = configuration.getTemplate("template" + req.getRequestURI().replaceAll(".html","ftl"));
                template.process(model,resp.getWriter());
            }catch (Exception e){ 
                if(e instanceof TemplateNotFoundException){ 
                    resp.getOutputStream().print("template not found");
                }else{ 
                    resp.getOutputStream().print(e.getMessage());
                }
            }
    
    
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            doRender(req,resp);
        }
    }

2.使用FreemarkServlet  
在启动类里面，添加freemarkerServlet

...
      		//添加filter
            context.addFilterDef(filterDef);
            context.addFilterMap(filterMap);
    		//这里注释调thymeleafServlet
            //addThymeleafServlet(context,tomcat);
            addFreemarkerServlet(context,tomcat);
            //启动tomcat
            tomcat.start();
            ...

3.addFreemarkerServlet方法

public static void addFreemarkerServlet(Context context,Tomcat tomcat){ 
            Wrapper servlet = Tomcat.addServlet(context, "FreemarkerServlet", new FreemarkerServlet());
            servlet.addMapping("*.html");
        }

4.创建对应的ftl模板文件  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 14]

<!doctype html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
        <meta http-equiv="X-UA-Compatible" content="ie=edge">
        <title>Document</title>
    </head>
    <body>
    this is freemarker page ${Request.getRequestURI()}
    </body>
    </html>

5.启动项目，通过浏览器访问  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 15]

#### 使用kotlin语言 ####

1.使用FreemarkServlet  
在启动类里面添加刚刚创建的FreemarkerServlet.java

...
        filterMap.addURLPattern("/*")
        filterMap.filterName = "CharacterFilterEncoding"
    
        context.addFilterDef(filterDef)
        context.addFilterMap(filterMap)
    
        //addThymeleafServlet(context)
    
        addFreemarkerServlet(context)
    
        tomcat.start()
    }
    //这里是函数
    fun addFreemarkerServlet(context:Context){ 
        val servlet = Tomcat.addServlet(context, "FreemarkerServlet", FreemarkerServlet())
        servlet.addMapping("*.html")
    }
    ...

2.启动项目，通过浏览器访问  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNDEzMDEx_size_16_color_FFFFFF_t_70 16]  
![在这里插入图片描述][20210430205513972.png]

# 完整代码 #

## java语言 ##

FreemarkerServlet.java

package com.lhstack.embed.servlet;
    
    import freemarker.template.Configuration;
    import freemarker.template.Template;
    import freemarker.template.TemplateNotFoundException;
    
    import javax.servlet.ServletConfig;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.util.HashMap;
    import java.util.Locale;
    import java.util.Map;
    
    /** * @author lhstack */
    public class FreemarkerServlet extends HttpServlet { 
    
        private Configuration configuration = null;
    
        @Override
        public void init(ServletConfig config) throws ServletException { 
            configuration = new Configuration(Configuration.VERSION_2_3_31);
            configuration.setClassLoaderForTemplateLoading(config.getServletContext().getClassLoader(),"");
            configuration.setEncoding(Locale.CHINA,"UTF-8");
            configuration.setDefaultEncoding("UTF-8");
        }
    
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            doRender(req,resp);
        }
    
        /** * 统一渲染方法 * @param req * @param resp */
        private void doRender(HttpServletRequest req, HttpServletResponse resp) throws IOException { 
            //创建用于模板引擎中使用的变量
            Map<String,Object> model = new HashMap<>(4);
            model.put("Request",req);
            model.put("Response",resp);
            model.put("Session",req.getSession());
            model.put("Context",req.getServletContext());
            resp.setContentType("text/html;charset=utf-8");
            try{ 
                Template template = configuration.getTemplate("template" + req.getRequestURI().replaceAll(".html",".ftl"));
                template.process(model,resp.getWriter());
            }catch (Exception e){ 
                if(e instanceof TemplateNotFoundException){ 
                    resp.getOutputStream().print("template not found");
                }else{ 
                    resp.getOutputStream().print(e.getMessage());
                }
            }
    
    
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            doRender(req,resp);
        }
    }

EmbedTomcatApplication.java

package com.lhstack.embed;
    
    import com.lhstack.embed.servlet.FreemarkerServlet;
    import org.apache.catalina.Context;
    import org.apache.catalina.Wrapper;
    import org.apache.catalina.startup.Tomcat;
    import org.apache.tomcat.util.descriptor.web.FilterDef;
    import org.apache.tomcat.util.descriptor.web.FilterMap;
    import org.thymeleaf.TemplateEngine;
    import org.thymeleaf.context.WebContext;
    import org.thymeleaf.templateresolver.ServletContextTemplateResolver;
    
    import javax.servlet.*;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    /** * @author lhstack */
    public class EmbedTomcatApplication { 
        public static void main(String[] args) throws Exception { 
            //tomcat监听端口
            int port = 8080;
    // //tomcat的baseDir，如果是内嵌的，不需要启动war包项目，可以不需要设置此参数,这里就说明一下，不做配置
    // String baseDir = System.getProperty("user.dir") + "/tomcat";
    // //这里tomcat需要读取baseDir下面的webapps目录，并不会自动创建，所以需要单独处理一下，如果不需要启动war包项目，可以不做配置
    // String webapps = baseDir + "/webapps";
    // //创建目录
    // File file = new File(webapps);
    // if(!file.exists()){ 
    // file.mkdirs();
    // }
            Tomcat tomcat = new Tomcat();
            //tomcat.setBaseDir();
    
            tomcat.setPort(port);
            //需要设置一下端口，不然无法访问
            tomcat.getConnector().setPort(port);
    
            //创建一个context
            Context context = tomcat.addContext("/", Thread.currentThread().getContextClassLoader().getResource("").getFile());
    
            //创建servlet，指向上面创建的context,通过contextPath判断
            Wrapper servlet = tomcat.addServlet("/", "HelloServlet", new HttpServlet() { 
                @Override
                protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
                    //修改之前的输出，这里为了测试模板引擎的功能，所以选择转发
                    req.getRequestDispatcher("index.html").forward(req,resp);
                }
            });
            //添加映射
            servlet.addMapping("/");
    
            String encoding = "UTF-8";
    
            //定义filter
            FilterDef filterDef = new FilterDef();
            filterDef.setFilterName("CharacterEncodingFilter");
            filterDef.setFilter((req, res, chain) -> { 
    
                if(req instanceof HttpServletRequest){ 
                    System.out.println("setting request character encoding");
                    req.setCharacterEncoding(encoding);
                }
                if(res instanceof HttpServletResponse){ 
                    System.out.println("setting response character encoding");
                    res.setCharacterEncoding(encoding);
                }
                chain.doFilter(req,res);
            });
    
            //定义filter映射
            FilterMap filterMap = new FilterMap();
            filterMap.setFilterName("CharacterEncodingFilter");
            filterMap.addURLPattern("/*");
    
            //添加filter
            context.addFilterDef(filterDef);
            context.addFilterMap(filterMap);
    
            //addThymeleafServlet(context,tomcat);
            addFreemarkerServlet(context,tomcat);
            //启动tomcat
            tomcat.start();
    
        }
    
        public static void addFreemarkerServlet(Context context,Tomcat tomcat){ 
            Wrapper servlet = Tomcat.addServlet(context, "FreemarkerServlet", new FreemarkerServlet());
            servlet.addMapping("*.html");
        }
    
        public static void addThymeleafServlet(Context context,Tomcat tomcat){ 
            //这里context上下文，thymeleaf会去加载context的docBase目录下面的资源，所以之前我在创建context时，添加了当前classpath路径作为docBase路径
            ServletContext servletContext = context.getServletContext();
            ServletContextTemplateResolver contextTemplateResolver = new ServletContextTemplateResolver(servletContext);
            TemplateEngine templateEngine = new TemplateEngine();
            templateEngine.addTemplateResolver(contextTemplateResolver);
            Tomcat.addServlet(context, "ThymeleafServlet", new HttpServlet() { 
                @Override
                protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
                    DispatcherType dispatcherType = req.getDispatcherType();
                    resp.setContentType("text/html;charset=utf-8");
                    try{ 
                        String html = null;
                        if(dispatcherType == DispatcherType.FORWARD){ 
                            //如果是forward，就转发到受保护的template目录下面
                            html = templateEngine.process("/template" + req.getRequestURI(),new WebContext(req,resp,servletContext));
                        }else if(dispatcherType == DispatcherType.REQUEST){ 
                            //如果是普通请求，就映射static目录
                            html = templateEngine.process("/static" + req.getRequestURI(),new WebContext(req,resp,servletContext));
                        }
                        resp.getOutputStream().print(html);
                    }catch (Exception e){ 
                        resp.getOutputStream().print("404 not found");
                    }
                }
            }).addMapping("*.html");
        }
    }

## kotlin语言 ##

package com.lhstack.embed
    
    import com.lhstack.embed.servlet.FreemarkerServlet
    import org.apache.catalina.Context
    import org.apache.catalina.session.StandardManager
    import org.apache.catalina.startup.Tomcat
    import org.apache.catalina.util.SessionIdGeneratorBase
    import org.apache.tomcat.util.descriptor.web.FilterDef
    import org.apache.tomcat.util.descriptor.web.FilterMap
    import org.thymeleaf.TemplateEngine
    import org.thymeleaf.context.WebContext
    import org.thymeleaf.templateresolver.ServletContextTemplateResolver
    import java.lang.Exception
    import java.util.*
    import javax.servlet.DispatcherType
    import javax.servlet.Filter
    import javax.servlet.http.HttpServlet
    import javax.servlet.http.HttpServletRequest
    import javax.servlet.http.HttpServletResponse
    
    fun main() { 
        val port:Int = 8080
        val tomcat:Tomcat = Tomcat()
        tomcat.setPort(port)
        tomcat.connector.port = port
        val context = tomcat.addContext("/", Thread.currentThread().contextClassLoader.getResource("")!!.path)
        val servlet = tomcat.addServlet("/", "HelloServlet", object : HttpServlet() { 
            override fun doGet(req: HttpServletRequest?, resp: HttpServletResponse?) { 
                //修改之前的输出，这里为了测试模板引擎的功能，所以选择转发
                req!!.getRequestDispatcher("index.html").forward(req,resp)
            }
        })
        servlet.addMapping("/")
    
        //添加context关联器
        context.manager = StandardManager()
    
        context.manager.sessionIdGenerator = object:SessionIdGeneratorBase(){ 
            override fun generateSessionId(route: String?): String { 
                return "lhstack->uuid->${UUID.randomUUID().toString().replace("-","")}"
            }
        }
    
        val encoding = "UTF-8"
    
        val filterDef = FilterDef()
        filterDef.filterName = "CharacterFilterEncoding"
        filterDef.filter = Filter {  req, res, chain ->
            if(req is HttpServletRequest){ 
                println("setting request character encoding $encoding")
                req.characterEncoding = encoding
            }
            if(res is HttpServletResponse){ 
                println("setting response character encoding $encoding")
                res.characterEncoding = encoding
            }
            chain.doFilter(req,res)
        }
    
        val filterMap = FilterMap()
    
        filterMap.addURLPattern("/*")
        filterMap.filterName = "CharacterFilterEncoding"
    
        context.addFilterDef(filterDef)
        context.addFilterMap(filterMap)
    
        //addThymeleafServlet(context)
    
        addFreemarkerServlet(context)
    
        tomcat.start()
    }
    
    fun addFreemarkerServlet(context:Context){ 
        val servlet = Tomcat.addServlet(context, "FreemarkerServlet", FreemarkerServlet())
        servlet.addMapping("*.html")
    }
    
    fun addThymeleafServlet(context: Context){ 
        val servletContextTemplateResolver = ServletContextTemplateResolver(context.servletContext)
        val templateEngine = TemplateEngine()
        templateEngine.addTemplateResolver(servletContextTemplateResolver)
        Tomcat.addServlet(context,"ThymeleafServlet",object:HttpServlet(){ 
            override fun doGet(req: HttpServletRequest?, resp: HttpServletResponse?) { 
                val dispatcherType = req!!.dispatcherType
                resp!!.contentType = "text/html;charset=utf-8"
                try { 
                    var html: String? = null
                    if (dispatcherType == DispatcherType.FORWARD) { 
                        //如果是forward，就转发到受保护的template目录下面
                        html = templateEngine.process("/template" + req.requestURI, WebContext(req, resp, servletContext))
                    } else if (dispatcherType == DispatcherType.REQUEST) { 
                        //如果是普通请求，就映射static目录
                        html = templateEngine.process("/static" + req.requestURI, WebContext(req, resp, servletContext))
                    }
                    resp.outputStream.print(html)
                } catch (e: Exception) { 
                    resp.outputStream.print("404 not found")
                }
            }
        }).addMapping("*.html")
    
    }

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