项目场景：
CentOS 7.3
JDK: openjdk version “1.8.0_302”
Mysql 5.7.35
问题描述：
数据库链接错误
Communications link failure
Caused by: javax.net.ssl.SSLHandshakeException: No appropriate protocol (protocol is disabled or cipher suites are inappropriate)
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_302] at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_302] at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_302] at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_302] at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:351) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.protocol.a.NativeAuthenticationProvider.negotiateSSLConnection(NativeAuthenticationProvider.java:777) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.protocol.a.NativeAuthenticationProvider.proceedHandshakeWithPluggableAuthentication(NativeAuthenticationProvider.java:486) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.protocol.a.NativeAuthenticationProvider.connect(NativeAuthenticationProvider.java:202) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.protocol.a.NativeProtocol.connect(NativeProtocol.java:1442) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.NativeSession.connect(NativeSession.java:165) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:955) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:825) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] ... 6 common frames omitted Caused by: javax.net.ssl.SSLHandshakeException: No appropriate protocol (protocol is disabled or cipher suites are inappropriate) at sun.security.ssl.HandshakeContext.<init>(HandshakeContext.java:171) ~[na:1.8.0_302] at sun.security.ssl.ClientHandshakeContext.<init>(ClientHandshakeContext.java:98) ~[na:1.8.0_302] at sun.security.ssl.TransportContext.kickstart(TransportContext.java:220) ~[na:1.8.0_302] at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:428) ~[na:1.8.0_302] at com.mysql.cj.protocol.ExportControlled.performTlsHandshake(ExportControlled.java:315) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.protocol.StandardSocketFactory.performTlsHandshake(StandardSocketFactory.java:188) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.protocol.a.NativeSocketConnection.performTlsHandshake(NativeSocketConnection.java:99) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:347) ~[mysql-connector-java-8.0.13.jar!/:8.0.13] ... 13 common frames omitted
原因分析：
没有支持的SSL协议
因为我数据库配置时是要用SSL的
url: jdbc:mysql://localhost:3306/db_xxx?useUnicode=true&characterEncoding=utf-8&useSSL=true&serverTimezone=CTT
解决方案：
方案一 连接时关闭useSSL 即设置为useSSL=false
url: jdbc:mysql://localhost:3306/db_xxx?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=CTT
方案二 JDK
找到jdk/jre/lib/security/java.security文件
（centos7.3 路径是/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.302.b08-0.el7_9.x86_64/jre/lib/security）
修改
# jdk.tls.disabledAlgorithms=MD5, SSLv3, DSA, RSA keySize < 2048 jdk.tls.disabledAlgorithms=SSLv3, TLSv1, TLSv1.1, RC4, DES, MD5withRSA, \ DH keySize < 1024, EC keySize < 224, 3DES_EDE_CBC, anon, NULL, \ include jdk.disabled.namedCurves
为
# jdk.tls.disabledAlgorithms=SSLv3, TLSv1, TLSv1.1, RC4, DES, MD5withRSA, \ jdk.tls.disabledAlgorithms=RC4, DES, MD5withRSA, \ DH keySize < 1024, EC keySize < 224, 3DES_EDE_CBC, anon, NULL, \ include jdk.disabled.namedCurves
保存再重启项目即可
