[ERROR] Failed to execute goal org.apache.maven.plugins:maven-war-plugin:2.1.1:war

创建springboot项目，且不采用<parent>引入springboot时，pom.xml如下：

<?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.example</groupId>
<artifactId>demo-without-parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>war</packaging>

    <name>demo-without-parent</name>
    <description>Demo project for Spring Boot</description>

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

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>2.0.2.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

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

执行

mvn clean install 

控制台报错：

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-war-plugin:2.1.1:war

原因：当设置为war时，web.xml必须存在。

解决：可通过插件配置属性将其忽略。

首先，spring-boot-dependencies 这个pom文件，找到

<maven-war-plugin.version>3.1.0</maven-war-plugin.version>

找到版本号是3.1.0

然后，在项目的pom.xml中，加入

<plugin>
    <artifactId>maven-war-plugin</artifactId>
    <version>3.1.0</version>
</plugin>

版本号必须与spring-boot-dependencies中maven-war-plugin-version版本号一致。

再次运行mvn clean install ，提示打包成功。

在idea中，运行启动类，成功启动。但是

java -jar demo-without-parent-0.0.1-SNAPSHOT.war

提示：demo-without-parent-0.0.1-SNAPSHOT.war中没有主清单属性

因为，maven-war-plugin的确执行了，但是spring-boot-maven-plugin插件却没有执行，原因在于该插件未指定版本，故设置版本号，依旧是从spring-boot-dependencies中找对应的版本号：2.0.2.RELEASE

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <version>2.0.2.RELEASE</version>
    <executions>
        <execution>
            <goals>
                <goal>repackage</goal>
            </goals>
        </execution>
    </executions>
</plugin>

重新执行

mvn clean install ，

mvn clean install
java -jar demo-without-parent-0.0.1-SNAPSHOT.war

成功。

最后总结：

1）、maven-war-plugin插件新老版本差异：
    2.2：项目中WEB-INF下必须存在web.xml
    3.1.0:不需要依赖web.xml
    而且，版本号必须与所引入的spring-boot-dependencies下的maven-war-plugin版本号一致。

2）、spring-boot-maven-plugin插件需要配置repackage，否则不会添加spring boot 引导依赖，进而无法引导当前应用。

3）、根据使用习惯通常不会采用spring-boot-dependencies

附，完整pom.xml

<?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.example</groupId>
<artifactId>demo-without-parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>war</packaging>

    <name>demo-without-parent</name>
    <description>Demo project for Spring Boot</description>

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

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>2.0.2.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </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>
                <version>2.0.2.RELEASE</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <artifactId>maven-war-plugin</artifactId>
                <version>3.1.0</version>
            </plugin>
        </plugins>
    </build>

</project>