The error message is as follows:
E/AndroidRuntime: FATAL EXCEPTION: Thread-4
Process: com.example.NCEPU, PID: 19597
java.lang.NoClassDefFoundError: Failed resolution of: Ljava/sql/SQLType;
at com.mysql.cj.jdbc.DatabaseMetaData.getInstance(DatabaseMetaData.java:746)
at com.mysql.cj.jdbc.ConnectionImpl.getMetaData(ConnectionImpl.java:1170)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:447)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:197)
at java.sql.DriverManager.getConnection(DriverManager.java:580)
at java.sql.DriverManager.getConnection(DriverManager.java:218)
at com.example.NCEPU.Utils.MySQLUtil$1.run(MySQLUtil.java:20)
at java.lang.Thread.run(Thread.java:929)
Caused by: java.lang.ClassNotFoundException: Didn't find class "java.sql.SQLType" on path: DexPathList[[zip file "/data/app/com.example.NCEPU-ONfkLzQBKVHb0mVXKR3p5g==/base.apk"],nativeLibraryDirectories=[/data/app/com.example.NCEPU-ONfkLzQBKVHb0mVXKR3p5g==/lib/arm64, /data/app/com.example.NCEPU-ONfkLzQBKVHb0mVXKR3p5g==/base.apk!/lib/arm64-v8a, /system/lib64, /system/product/lib64, /hw_product/lib64, /system/product/lib64]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:196)
at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
at com.mysql.cj.jdbc.DatabaseMetaData.getInstance(DatabaseMetaData.java:746)
at com.mysql.cj.jdbc.ConnectionImpl.getMetaData(ConnectionImpl.java:1170)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:447)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:197)
at java.sql.DriverManager.getConnection(DriverManager.java:580)
at java.sql.DriverManager.getConnection(DriverManager.java:218)
at com.example.NCEPU.Utils.MySQLUtil$1.run(MySQLUtil.java:20)
at java.lang.Thread.run(Thread.java:929)
W/libEGL: EGLNativeWindowType 0x6f3882b950 disconnect failed
I/Process: Sending signal. PID: 19597 SIG: 9
Problem analysis: The mysql jar package version is too high. I originally used the latest version: mysql-connector-java-8.0.21.jar, load the driver:
Class.forName("com.mysql.cj.jdbc.Driver");
String url = "jdbc:mysql://你的ip:端口号/表名?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
connection = DriverManager.getConnection(url, user, password);
The problem is solved: the jar version is lower. Here I use the mysql-connector-java-5.1.49.jar downloaded from the official website. Note that after changing to a lower version, the driver will become:
Class.forName("com.mysql.jdbc.Driver");