spring-boot建立最簡單的web應用

時間 2019-11-10

標籤 spring boot 建立最簡單 web 應用欄目 Spring 简体版

原文原文鏈接

初衷

看了一下spring-boot相關的書籍，建立一個hello world!的應用，是那麼的簡單。然而，本身動手，卻很不同。java

首先，咱們只是建立一個簡單的hello world!並不打算使用默認的thymeleaf，而是使用傳統的jsp。
固然，咱們不能把本身限制於一個簡單的hello world!咱們要的是具備熱部署功能的！web

spring-boot + 內置tomcat + jsp

1、初始化項目：

咱們只是構建一個hello world！的web應用。
打包方式選擇war
起步依賴只須要選擇Web和DevTools便可。spring

2、處理jsp目錄

springboot默認提供thymeleaf的模板，對於從傳統web開發轉過來的人來講，不喜歡！
然而 spring boot並無給咱們初始化webapp目錄。因此，仍是手動吧。apache

在「src/main」下建立「webapp/WEB_INF/jsp」目錄
而且在webapp目錄下新建index.jsp，內容爲hello world頁面。
注意是webapp目錄下，不是「webapp/WEB-INF/jsp」目錄。api

題外話：若是你甘願hello world!那就hello吧，反正我是 change the world!

3、處理pom.xml（添加jsp支持、war的插件）

一、而後添加jsp須要的依賴jstl

<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
</dependency>

二、jsp編譯須要的依賴

<dependency>
<groupId>org.apache.tomcat.embed</groupId>
<artifactId>tomcat-embed-jasper</artifactId>
</dependency>

三、把spring-boot-starter-tomcat的provided屬性註釋掉

四、再添加一個插件(因爲選擇的是war包方式)

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <configuration>
        <useSystemClassLoader>false</useSystemClassLoader>
    </configuration>
</plugin>

4、配置application.properties

server.port=9090

spring.thymeleaf.cache=false
spring.thymeleaf.enabled=false
spring.mvc.view.prefix=/
spring.mvc.view.suffix=.jsp

5、啓動應用

執行main方法啓動應用
啓動後訪問localhost:9090便可tomcat

6、處理完後的pom.xml是先這樣子的

<?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/4.0.0http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.lgh</groupId>
    <artifactId>sample</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>

    <name>sample</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <!--<scope>provided</scope>-->
        </dependency>
        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-jasper</artifactId>
            <!--<scope>provided</scope>-->
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <configuration>
                    <useSystemClassLoader>false</useSystemClassLoader>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

spring-boot + 外置tomcat + jsp

1、一樣的方式初始化項目

2、一樣的方式處理jsp目錄

3、處理pom.mxl（添加jsp支持、war插件及排除掉）

一、而後添加jsp須要的依賴jstl

<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
</dependency>

二、start-web排除掉tomcat

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>

三、添加servlet-api

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>3.1.0</version>
    <scope>provided</scope>
</dependency>

四、刪除spring-boot-starter-tomcat依賴

五、一樣添加一個插件

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <configuration>
        <useSystemClassLoader>false</useSystemClassLoader>
    </configuration>
</plugin>

4、一樣的配置application.properties

5、啓動應用

(idea中)在run/debug configuration窗口中，添加tomcatServer，配置部署便可
注意這種方式，application.properties中的server.port是不生效的。springboot

6、處理完後的pom.xml是先這樣子的

<?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.lgh</groupId>
    <artifactId>client</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>

    <name>client</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-tomcat</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
        </dependency>
    
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <fork>true</fork>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <configuration>
                    <useSystemClassLoader>false</useSystemClassLoader>
                </configuration>
            </plugin>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>


</project>

踩過的坑，吃過的屎

沒有熱部署，特別難受

一、添加一個依賴（初始化時若是選了就不須要手動添加了）

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <scope>runtime</scope>
</dependency>

二、插件添加配置（裏面的configuration節點加上）

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <fork>true</fork>
    </configuration>
</plugin>

添加了上面的兩個配置後，修改java代碼後，idea中能夠右鍵recompile從新編譯
若是是在本地tomcat的狀況下，idea會提示reload class。
若是是在spring boot內置的tomcat的狀況下，應用會自動重啓。mvc

不一樣的引導方式，不一樣的報錯信息

首先，咱們用idea建立的項目中，pom.xml文件是長這樣的app

<?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/4.0.0http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.lgh</groupId>
    <artifactId>sample</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>

    <name>sample</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>


</project>

爲了支持jsp，咱們加入兩個依賴webapp

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>jstl</artifactId>
</dependency>

<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-jasper</artifactId>
    <scope>provided</scope>
</dependency>

因爲咱們選擇了war的打包方式，你會發現，自動建立了一個ServletInitializer類。
因爲是war，還須要添加一個插件

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <configuration>
        <useSystemClassLoader>false</useSystemClassLoader>
    </configuration>
</plugin>

咱們再src/main下建立「webapp」目錄，並建立一個index.jsp文件
（還要去配置application.properties文件，把默認的模板禁用掉）

以上步驟是大部分博客的過程。這時候，咱們直接用main方法的方式啓動時，是醬紫的

解決辦法是：
把pom文件中的spring-boot-starter-tomcat 和 tomcat-embed-jasper的 provided屬性註釋掉。
註釋掉後，啓動起來，訪問localhost:8080便可看到hello world!

回到註釋provided屬性前，若是這時候咱們把ServletInitializer註釋掉
把Application類繼承SpringBootServletInitializer，像這樣子

@SpringBootApplication
public class ClientApplication extends SpringBootServletInitializer{

@Override
protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
    return application.sources(ClientApplication.class);
}

public static void main(String[] args) {
    SpringApplication.run(ClientApplication.class, args);
}

}

此時執行main方法啓動應用，報錯以下
org.springframework.beans.factory.BeanDefinitionStoreException: Failed to parse configuration class [com.lgh.client.ClientApplication]; nested exception is java.lang.IllegalStateException: Failed to introspect annotated methods on class org.springframework.boot.web.servlet.support.SpringBootServletInitializer