SpringBoot配置对jsp的支持

背景

随着模板技术的兴起，以简洁和约定大于配置的springboot框架不再内置对jsp的支持，而是通过模板技术thymeleaf,freemark等。但是有些场景需要jsp，又想用springboot，怎么办呢？接下来，通过配置是可以实现的

POM

这里，我将我的pom配置文件贴上来，大家可以只拷贝<dependencies>里面的依赖

<?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.tangbaobao</groupId>
    <artifactId>spring_boot_study</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>

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

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.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</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </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-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
        </dependency>
        <!-- Provided -->
        <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>
    </dependencies>

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

解释

When running a Spring Boot application that uses an embedded servlet container (and is packaged as an executable archive), there are some limitations in the JSP support.
• With Jetty and Tomcat, it should work if you use war packaging. An executable war will work when launched with java -jar, and will also be deployable to any standard container. JSPs are not supported when using an executable jar.

大概就是springboot本身不支持jsp，通过配置，可以让tomcat，jetty支持，但是Undertow容器不支持jsp，所有pom依赖中需要有jsp和tomcat的依赖

代码

项目structure

配置启动类

package com.tangbaobao.spring_boot_study;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;

@SpringBootApplication
public class SpringBootStudyApplication extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
        return builder.sources(SpringBootStudyApplication.class);
    }

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

注意：之所以要继承SpringBootServletInitializer这个类，在servlet3.0之后，支持注解配置，所以spring对其进行了封装，我们不用配置web.xml,继承此类，并将相应的bean穿进去，会自动扫描，配置。

编写controller

package com.tangbaobao.spring_boot_study.jsp;

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

import java.util.Map;

/**
 * @author tangxuejun
 * @version 2018/7/22 下午10:20
 */
@Controller
public class TestWithJsp {
    @RequestMapping("/hello")
    public String testJsp(Map<String, Object> map) {
        map.put("message", "hello jsp");
        return "welcome";
    }
}

jsp

<%@ page contentType="text/html; charset=utf-8" pageEncoding="utf-8" %>
<!DOCTYPE html>

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<html lang="en">

<body>
<br>
<br>
Message: ${message}
</body>

</html>

结果