问题1

Project build error: Non-resolvable parent POM for com.example0.0.1-SNAPSHOT: Failure to transfer org.springframework.boot:spring-
boot-starter-parent2.1.9.RELEASE from https://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be
reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer artifact
org.springframework.bootpom:2.1.9.RELEASE from/to central (https://repo.maven.apache.org/maven2):
sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find
valid certification path to requested target and ‘parent.relativePath’ points at no local POM

在这里插入图片描述

解决方案1

访问 https://repo.maven.apache.org/maven2 ，由于 https的地址左侧都会有个锁标记（绿色代表有该证书合法，红色代表不合法），点击小锁，弹出对话框。在 “连接”栏，单击右侧箭头，显示连接细节

单击“更多信息”，弹出“页面信息”对话框
![在这里插入图片描述](https://img-blog.csdnimg.cn/20191010122640396.png)切换到“安全”选项卡，点击"查看证书"，弹出"证书查看器"对话框
切换到“详细信息”选项卡，单击“导出”按钮导出证书。
导出的是 crt 后缀的证书文件

以管理员身份打开cmd，进入到 C:\Program Files\Java\jdk1.8.0_201\jre\lib\security 目录下，执行命令 keytool -keystore cacerts -importcert -alias 【证书文件名】 -file 【crt文件路径】，这里会要求你输入口令，默认的口令是 changeit。

口令也可以通过 -storepass changeit 直接指定
证书文件别名按照原文件名即可，我这里重命名了，导致导入不成功

在这里插入图片描述
最后会询问是否信任，直接回车即可。

解决方案2

创建一个 InstallCert.java类，添加如下代码

package javaDemo;
/*
 * Copyright 2006 Sun Microsystems, Inc.  All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Sun Microsystems nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.security.KeyStore;
import java.security.MessageDigest;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLException;
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;
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);
        }
    }
}

在 run configurations 对话框中添加如下配置
在这里插入图片描述运行程序，会打印如下

直接回车即可

将证书拷贝到$JAVA_HOME/jre/lib/security目录下，重新编译即可

解决方案3

换一个 workspace，新建项目

问题2

Failure to transfer org.springframework.bootpom:2.1.6.RELEASE from https://repo.maven.apache.org/maven2 was cached in the
local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer
artifact org.springframework.bootpom:2.1.6.RELEASE from/to central (https://repo.maven.apache.org/maven2):
repo.maven.apache.org

解决方案

上面说明使用的是本地仓库缓存下来的包，但缓存的包有问题，因此只能删除 repository 目录下的所有的包，然后 clean 项目，让其重新构建了。

补充

如果不是公司装的代理服务器把证书换了导致不能访问。可能是当前版本的JDK太旧了，已不再支持，可以卸载，然后装一个新版的，装完之后重启电脑试试。

jre11 开始，安装 jdk 之后，虽然jdk自带 jre，但目录下却没有原本的 jre 文件夹，这导致很多依赖于 jre 的软件都无法正常运行。可以使用命令 bin\jlink.exe --module-path jmods --add-modules java.desktop --output jre 在 jdk 目录下生成 jre 文件夹