列表返回的 JAVA JDBC 问题
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【中文标题】列表返回的 JAVA JDBC 问题【英文标题】：JAVA JDBC issues with List Return 【发布时间】：2018-07-02 18:19:20 【问题描述】：长期潜伏者。我一直在使用 Java 尝试执行我拥有的这个 JDBC SQL 语句，并且有时可以将结果运行类作为静态 void。当我尝试将结果集放入列表并返回时，我会在底部附加错误日志。如果我没有正确发布某些内容，我会事先道歉。奇怪的是我错过了一些东西，但似乎无法让我的眼睛注意到它。
提前致谢
附：温柔点，我是第一次。
珠光宝气
///////////////调用SQL事件的主Activity//////////////////// //
protected void onCreate(Bundle savedInstanceState)
int SDK_INT = android.os.Build.VERSION.SDK_INT;
if (SDK_INT > 8)
StrictMode.ThreadPolicy policy = new
StrictMode.ThreadPolicy.Builder()
.permitAll().build();
StrictMode.setThreadPolicy(policy);
//your codes here
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
SQLEvent EVENTS = new SQLEvent();
List<List<String>> EventString = EVENTS.main();
System.out.println("EVENT RESULTS: " + EventString);
///////////////SQL事件////////////////////////////////////////////////////////// p>
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
public class SQLEvent
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://***.***.***.***:3306/DB_NAME?useSSL=false&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC";
// Database credentials
static final String USER = "*******";
static final String PASS = "*******";
public List <List<String>> main()
ResultSet rs = null;
Connection conn = null;
java.sql.PreparedStatement stmt = null;
List<List<String>> result = new ArrayList<>();
try
//STEP 2: Register JDBC driver
Class.forName("com.mysql.cj.jdbc.Driver").newInstance();
//STEP 3: Open a connection
System.out.println("Connecting to database...");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
//STEP 4: Execute a query
System.out.println("Creating statement...");
String sql = "SELECT * FROM events WHERE LOC= ?";
stmt = conn.prepareStatement(sql);
//Bind values into the parameters.
stmt.setString(1, "matts office"); // This would set age
// Let us update age of the record with ID = 102;
//int rows = stmt.executeUpdate();
// System.out.println("Rows impacted : " + rows );
// Let us select all the records and display them.
// sql = "SELECT id, first, last, age FROM Employees";
// stmt.setInt(1, 1001);
rs = stmt.executeQuery();
int numcols = rs.getMetaData().getColumnCount();
//STEP 5: Extract data from result set
while (rs.next())
List<String> row = new ArrayList<>(numcols); // new list per row
int i = 1;
while (i <= numcols) // don't skip the last column, use <=
row.add(rs.getString(i++));
result.add(row); // add it to the result
//Retrieve by column name
int id = rs.getInt("id");
String LOC = rs.getString("LOC");
String EventName = rs.getString("EventName");
String EventDesc = rs.getString("EventDesc");
String Closed = rs.getString("Closed");
String TimeStart = rs.getString("TimeStart");
String TimeEnd = rs.getString("TimeEnd");
//Display values
System.out.print("ID: " + id);
System.out.print(", Location: " + LOC);
System.out.print(", Event Name: " + EventName);
System.out.println(", Event Description: " + EventDesc);
System.out.println(", Closed: " + Closed);
System.out.println(", Time Start: " + TimeStart);
System.out.println(", Time End: " + TimeEnd);
//STEP 6: Clean-up environment
if (!rs.next())
else
// MainActivity MA = new MainActivity();
// MA.NotificationEvent();
stmt.close();
conn.close();
System.out.println("Result Set: " + result);
rs.close();
catch (SQLException se)
//Handle errors for JDBC
se.printStackTrace();
catch (Exception e)
//Handle errors for Class.forName
e.printStackTrace();
finally
//finally block used to close resources
try
if (stmt != null)
stmt.close();
catch (SQLException se2)
// nothing we can do
try
if (conn != null)
conn.close();
catch (SQLException se)
se.printStackTrace();
//end finally try
//end try
System.out.println("Goodbye!");
return result;
//////////////////错误日志///////////////////// ///////////////
07-02 18:02:43.286 11991-11991/com.internalpositioning.find3.find3app E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.internalpositioning.find3.find3app, PID: 11991
java.lang.BootstrapMethodError: Exception from call site #145 bootstrap method
at com.mysql.cj.conf.ConnectionUrl.buildConnectionStringCacheKey(ConnectionUrl.java:236)
at com.mysql.cj.conf.ConnectionUrl.getConnectionUrlInstance(ConnectionUrl.java:167)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:201)
at java.sql.DriverManager.getConnection(DriverManager.java:569)
at java.sql.DriverManager.getConnection(DriverManager.java:219)
at com.internalpositioning.find3.find3app.SQLEvent.main(SQLEvent.java:45)
at com.internalpositioning.find3.find3app.MainActivity.onCreate(MainActivity.java:144)
at android.app.Activity.performCreate(Activity.java:7009)
at android.app.Activity.performCreate(Activity.java:7000)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Caused by: java.lang.NoClassDefFoundError: Invalid descriptor: VIIIIIIIIII.
at com.mysql.cj.conf.ConnectionUrl.buildConnectionStringCacheKey(ConnectionUrl.java:236)
at com.mysql.cj.conf.ConnectionUrl.getConnectionUrlInstance(ConnectionUrl.java:167)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:201)
at java.sql.DriverManager.getConnection(DriverManager.java:569)
at java.sql.DriverManager.getConnection(DriverManager.java:219)
at com.internalpositioning.find3.find3app.SQLEvent.main(SQLEvent.java:45)
at com.internalpositioning.find3.find3app.MainActivity.onCreate(MainActivity.java:144)
at android.app.Activity.performCreate(Activity.java:7009)
at android.app.Activity.performCreate(Activity.java:7000)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
【问题讨论】：
【参考方案1】：我想您的 MySQL 驱动程序版本不适用于 Android。看起来，它在Collectors.joining 上失败了。这是在 Java 8 中添加的。
另外，在我看来，直接从 Android 连接到数据库很奇怪。据我所知，通常移动应用程序会向有权访问数据库的后端层发出一些请求（通常是 REST）。
【讨论】：
感谢您的帮助！我会调查的。以上是关于列表返回的 JAVA JDBC 问题的主要内容，如果未能解决你的问题，请参考以下文章
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