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how to add dom4j dependecy in maven pom with spring boot

I want to use dom4j to parse xml string. But when I add dom4j dependency in pom file, my dev tool(Eeclipse) prompt errors below:
I tried to refresh project and maven's update project, the errors still occured. If remove the dependency, all of errors disappear, also dom4j cannot use.
Eclipse version:
Eclipse Java EE IDE for Web Developers.
Version: Photon Release (4.8.0)
Build id: 20180619-1200
POM file:
http://maven.apache.org/xsd/maven-4.0.0.xsd">
4.0.0
<groupId>test</groupId>
<artifactId>test</artifactId>
<version>1.0.0</version>
<packaging>jar</packaging>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.3.RELEASE</version>
</parent>
<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>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
</dependency>
<dependency>
<groupId>dom4j</groupId>
<artifactId>dom4j</artifactId>
</dependency>
</dependencies>
<properties>
<java.version>1.8</java.version>
</properties>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
Maven Version:

I figured out it through a whole day working, the fix steps are:
1. the first line of errors prompt in eclipse is : fail to read artifact descriptor for xml-apis:xml-apis:jar:1.4.01.(the first capture image of the question)
2. I assumed that something are wrong with xml-apis in maven repository, so I find the directory of xml-apis in maven repository and remove them all
3. After that, I use Maven->Update project in eclipse, the errors run away.
I think the reason is: some files of xml-apis were damaged.

Create war file from Spring:boot project in Eclipse

I am pretty new to Spring Boot and I have completed a application that works well on my localhost. As I have been told to deploy it outside my localhost on for example a webbhotel or simular I need to export the project as a war-file and not as a jar-file.
UPDATE!!
I run the project as a Springproject generated in Spring Initialzr and using Eclipse as a IDE.
In Eclipse I have followed the steps
<packaging>war</packaging>
and
<dependencies>
<!-- … -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
</dependency>
<!-- … -->
</dependencies>
from Spring Boot Referencepage
https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#howto-create-a-deployable-war-file
In my project I use
<dependency>
<groupId>org.apache.tomcat.embed</groupId>
<artifactId>tomcat-embed-jasper</artifactId>
<scope>provided</scope>
</dependency>
Do I need to add the sprinng-boot-starter-tomcat dependency and add provided to that on aswell as tomcat-embed-jasper so that my dependency will be like this?
<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-tomcat</artifactId>
<scope>provided</scope>
</dependency>
When I try to export to war-file in Eclipse, Eclipse can't find my project. It can find it if I try to export Java>JAR FILE but not if I try Web>WAR FILE
Do anyone know what I am doing wrong and if it is neccesary to export to a WAR-file to deploy to a external server?

You need to extend ****SpringBootServletInitializer**** in your #SpringBootApplication
You don't need to add the ****sprinng-boot-starter-tomcat**** dependency for war file generation
Use below configuration in pom.xml
<packaging>war</packaging>
Configure Build Path for your project and select JDK
Right click on project > Run As > Maven Install
It will generate the war file inside target folder.
Copy this war and deploy to any web/application server (I have renamed it to demo.war).
You can access the app by using your host name followed by the port and app name.

To generate WAR file in STS (Spring Tools Suite):
Run as-> Maven Install

After change to <packaging>war</packaging> in pom.xml.
utilize the command: mvn package

You can also proceed by selecting menus File -> Export -> Web -> War file

I generated a war file by the following steps:
Add above dependency.
Open command prompt.
cd into your project directory.
Run the command: mvn clean install.
Then a war file will be generated in the target directory.

If you are using maven, you can add tag to specify the type we want to create - jar or war. After that in sts you trigger a maven build and specify the goals - clean install and specify the number of threads you want to run for the build. In case you want to skip the test case you can give skipTest =true, or if you to run from command prommpt you can give -Dmaven.test.skip=true.
Once done, war file will be generated under target folder. (unless we specify a specific deployment folder)

Step1:- Create ServletInitializer file by extending SpringBootServletInitializer
public class ServletInitializer extends SpringBootServletInitializer {
#Override
protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
return application.sources(DemoApplication.class);
}
}
Step2:- Use #SpringBootApplication in main class
#SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
Step3:- Package type as war in pom.xml
<packaging>war</packaging>
Step4:- Give build filename as like this
<build>
<finalName>demo</finalName>
</build>
Step5:- Add external tomcat dependency as provided scope
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
</dependency>
Note:- For reference purpose, I'm adding my completed 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.7.7</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>war</packaging>
<name>demo</name>
<description>Demo project for Spring Boot</description>
<properties>
<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-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>
<finalName>demo</finalName>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>

How to bundle/package latest version of custom library in maven web project without updating pom.xml?

I have a custom library - Dao.jar which contains the database persistence logic.
I push this jar to artifactory with new version each time there is a change in code as shown below :
mvn install:install-file -Dfile=C:\*****\target\Dao.jar -DgroupId=non-public.com.karthik -DartifactId=dao -Dversion=2.0 -Dpackaging=jar
I have another maven web project which has a dependency on this jar. This jar is also packaged/bundled in the maven webapp project/war.
<dependency>
<groupId>non-public.com.karthik</groupId>
<artifactId>dao</artifactId>
<version>2.0</version>
</dependency>
Currently, I am changing the version of dao dependency in the pom.xml & re-building the maven webapp project each time a new version of Dao.jar is available in the artifactory.
Is there any option to build the maven project with the latest version of Dao.jar without manually changing the dependency version in the pom.xml?

When Maven searches for a dependency, it first checks the local repository (~/.m2/repository). If it's not found, it tries other resources, such as remote repositories defined in the POM file or in the settings file (~/.m2/settings.xml).
By that logic, if you try to use a version of a local project that's not yet installed to the local repository, Maven will never be able to find it to use in another project.
To avoid changing version numbers all the time and manually building both projects. You could create a parent POM for both projects. The parent would then be able to recognize that one of the child projects depends on the other and build them in the correct order.

Based on Luciano's inputs, I have created a multi-module maven project/parent POM with 2 modules(dao & web)
Parent
<groupId>com.karthik</groupId>
<artifactId>test</artifactId>
<packaging>pom</packaging>
<version>1.0-SNAPSHOT</version>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>3.0.5.RELEASE</version>
</dependency>
<dependency>
<groupId>oracle</groupId>
<artifactId>ojdbc6</artifactId>
<version>11.2.0.3</version>
</dependency>
..........
</dependencies>
</dependencyManagement>
<modules>
<module>web</module>
<module>dao</module>
</modules>
Child module # 1 - dao
<parent>
<groupId>com.karthik</groupId>
<artifactId>test</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>dao</artifactId>
<packaging>jar</packaging>
<dependencies>
<dependency>
<groupId>oracle</groupId>
<artifactId>ojdbc6</artifactId>
</dependency>
.........
</dependencies>
Child module # 2 - web(declared dao dependency in POM)
<parent>
<groupId>com.karthik</groupId>
<artifactId>test</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>web</artifactId>
<packaging>war</packaging>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
</dependency>
<dependency>
<groupId>com.karthik</groupId>
<artifactId>dao</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
.........
</dependencies>
When I run mvn package command at root path of parent pom, both modules - web.war and dao.jar are built. This method ensures always the latest version of dao.jar is packaged in web.war.

Thymeleaf dependency causes "Error: Could not find or load main class" in Spring tool suite

I've just downloaded STS and started some maven project and it worked properly, but when I start using thymeleaf it doesn't work.
I see an exclamation mark on the project name, and I get this error Error: Could not find or load main class.
I tried adding its dependencies by myself in the POM, I get that error and it goes away once I remove them!
I also tried creating a "Spring Starter Project" and choosing dependencies "Web and Thymeleaf" to be added, right after the project is created I see a syntax error in the POM in the test dependency Failure to transfer org.springframework.boot:spring-boot-starter-test:jar
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
and when I remove it and its class, I get the same error above.
here is my POM now:
<?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-2</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>demo-2</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.4.2.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-thymeleaf</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

Try to update your maven repository, try first:
mvn dependency:purge-local-repository
Description:
When run on a project, remove the project dependencies from the local
repository, and optionally re-resolve them. Outside of a project,
remove the manually given dependencies.
and then try:
mvn dependency:copy-dependencies
Description:
Goal that copies the project dependencies from the repository to a
defined location.
It seems to me that your local Maven repository doesn't include the thymeleaf dependecy.

The problem was solved after removing failed downloads:
from CMD:
cd %userprofile%\.m2\repository
for /r %i in (*.lastUpdated) do del %i
then updating the project.
It re-downloaded the dependencies and it worked just fine.

In maven project How to download the library in source/binary, mentioned in the <parent> tag in POM file?

This is the pom file.
<project>
<parent>
<groupId>org.jboss.weld</groupId>
<artifactId>weld-api-bom</artifactId>
<version>1.0</version>
<relativePath>../bom/pom.xml</relativePath>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>my-module</artifactId>
<dependencies>
<dependency>
<groupId>javax.el</groupId>
<artifactId>el-api</artifactId>
<optional>true</optional>
</dependency>
</dependencies>
</project>
I know, to download the dependencies(above its "el-api") we should use
mvn dependency
But what is the command used to download the parent dependency(i.e weld-api-bom)?

Given your parent pom has
../bom/pom.xml
It could either be downloaded (if avaiable in configured repository) or be read from disk if it there.
In any case most of the maven commands will trigger the download of this artifact as one of the very first steps of the build.
Please also note that "mvn dependency" is not a valid command.