idea 使用maven报错已解决
maven核心思想：约束大于配置。
maven下载与安装，各位大侠写的都很好，所以直接上车：
下载安装：https://blog.csdn.net/c_staunch/article/details/100981699
maven教程：https://www.runoob.com/maven/maven-tutorial.html 或者看看 https://blog.csdn.net/lovequanquqn/article/details/81627807
在idea中使用maven：
1、新建项目时，选则maven。
2、 在下图选择使用自己安装的版本或者idea自带的版本
PS：idea在新建项目时，会将上面三个域重置为默认值。因为这时配置的是该项目中的选项，不是全局选项。
全局配置：file ---new projects settings---settingt for new projects,找到maven 进行设置；（PPS：不同idea版本，设置位置不同，貌似有的在other settings中）
3、正常创建后，就可以自动下载所需内容了。
4、创建完成后，项目目录（选择了webapp模板）
然而
在idea中创建maven项目时，插件全部不能下载：
报错信息如下：
Lifecycle-- clean-- run maven bilud时 报错信息如下：
D:\myeclipse18\jdk1.8.0_181\bin\java.exe -Dmaven.multiModuleProjectDirectory=D:\IDEA\maven01 -Dmaven.home=D:\Maven\apache-maven-3.6.3
-Dclassworlds.conf=D:\Maven\apache-maven-3.6.3\bin\m2.conf "-Dmaven.ext.class.path=D:\IDEA\IntelliJ IDEA 2020.3.2\plugins\maven\lib\maven-event-listener.jar"
"-javaagent:D:\IDEA\IntelliJ IDEA 2020.3.2\lib\idea_rt.jar=51697:D:\IDEA\IntelliJ IDEA 2020.3.2\bin"
-Dfile.encoding=UTF-8 -classpath D:\Maven\apache-maven-3.6.3\boot\plexus-classworlds-2.6.0.jar;
D:\Maven\apache-maven-3.6.3\boot\plexus-classworlds.license org.codehaus.classworlds.Launcher -Didea.version=2020.3.2
-s D:\Maven\apache-maven-3.6.3\conf\settings.xml clean [INFO] Scanning for projects... [INFO] [INFO] ------------------------< org.example:maven01 >------------------------- [INFO] Building maven01 1.0-SNAPSHOT [INFO] --------------------------------[ jar ]--------------------------------- Downloading from alimaven: http://maven.aliyun.com/nexus/content/repositories/central/org/apache/maven/plugins/maven-clean-plugin/2.5/maven-clean-plugin-2.5.pom [INFO] ------------------------------------------------------------------------ [INFO] BUILD FAILURE [INFO] ------------------------------------------------------------------------ [INFO] Total time: 0.964 s [INFO] Finished at: 2021-03-03T12:05:28+08:00 [INFO] ------------------------------------------------------------------------ [ERROR] Plugin org.apache.maven.plugins:maven-clean-plugin:2.5 or one of its dependencies could not be resolved: Failed to read artifact descriptor for
org.apache.maven.plugins:maven-clean-plugin:jar:2.5: Could not transfer artifact org.apache.maven.plugins:maven-clean-plugin:pom:2.5
from/to alimaven (http://maven.aliyun.com/nexus/content/repositories/central/):
Transfer failed for http://maven.aliyun.com/nexus/content/repositories/central/org/apache/maven/plugins/maven-clean-plugin/2.5/maven-clean-plugin-2.5.pom:
sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException:
unable to find valid certification path to requested target -> [Help 1] [ERROR] [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch. [ERROR] Re-run Maven using the -X switch to enable full debug logging. [ERROR] [ERROR] For more information about the errors and possible solutions, please read the following articles: [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginResolutionException Process finished with exit code 1
找了很多方法，检查很多遍settings文件，都不成。回头看报错
提取关键报错信息：
sun.security.validator.ValidatorException: PKIX path building failed:
sun.security.provider.certpath.SunCertPathBuilderException:
unable to find valid certification path to requested target -> [Help 1]-----关键
看起来是缺少某个证书，于是：https://www.cnblogs.com/xiaoping1993/p/9717649.html 或者 https://blog.csdn.net/faye0412/article/details/6883879
代码如下：
import java.io.*; import java.net.URL; import java.security.*; import java.security.cert.*; import javax.net.ssl.*; public class InstallCert { public static void main(String[] args) throws Exception { String host; int port; char[] passphrase; if ((args.length == 1) || (args.length == 2)) { String[] c = args[0].split(":"); host = c[0]; port = (c.length == 1) ? 443 : Integer.parseInt(c[1]); String p = (args.length == 1) ? "changeit" : args[1]; passphrase = p.toCharArray(); } else { System.out.println("Usage: java InstallCert <host>[:port] [passphrase]"); return; } File file = new File("jssecacerts"); if (file.isFile() == false) { char SEP = File.separatorChar; File dir = new File(System.getProperty("java.home") + SEP + "lib" + SEP + "security"); file = new File(dir, "jssecacerts"); if (file.isFile() == false) { file = new File(dir, "cacerts"); } } System.out.println("Loading KeyStore " + file + "..."); InputStream in = new FileInputStream(file); KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType()); ks.load(in, passphrase); in.close(); SSLContext context = SSLContext.getInstance("TLS"); TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm()); tmf.init(ks); X509TrustManager defaultTrustManager = (X509TrustManager)tmf.getTrustManagers()[0]; SavingTrustManager tm = new SavingTrustManager(defaultTrustManager); context.init(null, new TrustManager[] {tm}, null); SSLSocketFactory factory = context.getSocketFactory(); System.out.println("Opening connection to " + host + ":" + port + "..."); SSLSocket socket = (SSLSocket)factory.createSocket(host, port); socket.setSoTimeout(10000); try { System.out.println("Starting SSL handshake..."); socket.startHandshake(); socket.close(); System.out.println(); System.out.println("No errors, certificate is already trusted"); } catch (SSLException e) { System.out.println(); e.printStackTrace(System.out); } X509Certificate[] chain = tm.chain; if (chain == null) { System.out.println("Could not obtain server certificate chain"); return; } BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); System.out.println(); System.out.println("Server sent " + chain.length + " certificate(s):"); System.out.println(); MessageDigest sha1 = MessageDigest.getInstance("SHA1"); MessageDigest md5 = MessageDigest.getInstance("MD5"); for (int i = 0; i < chain.length; i++) { X509Certificate cert = chain[i]; System.out.println (" " + (i + 1) + " Subject " + cert.getSubjectDN()); System.out.println(" Issuer " + cert.getIssuerDN()); sha1.update(cert.getEncoded()); System.out.println(" sha1 " + toHexString(sha1.digest())); md5.update(cert.getEncoded()); System.out.println(" md5 " + toHexString(md5.digest())); System.out.println(); } System.out.println("Enter certificate to add to trusted keystore or 'q' to quit: [1]"); String line = reader.readLine().trim(); int k; try { k = (line.length() == 0) ? 0 : Integer.parseInt(line) - 1; } catch (NumberFormatException e) { System.out.println("KeyStore not changed"); return; } X509Certificate cert = chain[k]; String alias = host + "-" + (k + 1); ks.setCertificateEntry(alias, cert); OutputStream out = new FileOutputStream("jssecacerts"); ks.store(out, passphrase); out.close(); System.out.println(); System.out.println(cert); System.out.println(); System.out.println ("Added certificate to keystore 'jssecacerts' using alias '" + alias + "'"); } private static final char[] HEXDIGITS = "0123456789abcdef".toCharArray(); private static String toHexString(byte[] bytes) { StringBuilder sb = new StringBuilder(bytes.length * 3); for (int b : bytes) { b &= 0xff; sb.append(HEXDIGITS[b >> 4]); sb.append(HEXDIGITS[b & 15]); sb.append(' '); } return sb.toString(); } private static class SavingTrustManager implements X509TrustManager { private final X509TrustManager tm; private X509Certificate[] chain; SavingTrustManager(X509TrustManager tm) { this.tm = tm; } public X509Certificate[] getAcceptedIssuers() { throw new UnsupportedOperationException(); } public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException { throw new UnsupportedOperationException(); } public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException { this.chain = chain; tm.checkServerTrusted(chain, authType); } } }
命令行执行 Java InstallCert maven.aliyun.com
maven.aliyun.com 按需更换
输入1，回车，当前文件夹下得到证书文件，将其放入jre/lib/security目录下,也有的说放在jre\lib\ext 下，只好都放一下试试。
重启idea，重建maven项目，=一般人就好用了。
然而，我已经快无能为力了。开始怀疑是不是idea的问题？是不是maven3.6.3版本的问题？要不要降个版本？
于是cmd,mvn -v
what?
不是内部或外部命令，也不是可运行的程序
或批处理文件。
安装的时候，明明好用的,环境变量也没问题，不知道无意间做了什么骚操作。于是删了maven重装。
然后在命令行中验证：mvn help:system
build success！看到本地仓库中有了文件。但不是在自己创建的本地仓库repository,而是自行创建了一个repository1.
再从idea上创建，就没有问题了。
对不起大家，我撒谎了，虽然idea中可以使用maven项目，我还是没能彻底解决 PKIX path building failed: 的问题。
依赖的jar都得手动下载，放到库中。
https://www.cnblogs.com/fengyupinglan/p/14537223.html
用上面那个方式解决了一半，还是很麻烦？难道因为我用了破解版得idea而惩罚我么？
idea中的解决方法：https://www.cnblogs.com/fengyupinglan/p/14537223.html
