How Java obtains the fields and field types of a database

Java Gets the field names of the fields in the table of the database, with the following code:

Import java.sql.Connection;
Import Java.sql.DriverManager;
Import Java.sql.ResultSet;
Import java.sql.PreparedStatement;
Import Java.sql.ResultSetMetaData;
Import java.sql.SQLException;
public class Testdemo {
public static Connection getconnection () {
Connection conn = null;
try {
Class.forName ("Com.mysql.jdbc.Driver");
String url = "jdbc:mysql://database IP Address: 3306/database name";
String user = "Database user name";
String pass = "Database user password";
conn = drivermanager.getconnection (URL, user, pass);
} catch (ClassNotFoundException e) {
E.printstacktrace ();
} catch (SQLException e) {
E.printstacktrace ();
}
Return conn;
}
public static void Main (string[] args) {
Connection conn = getconnection ();
String sql = "SELECT * from AccessType";
PreparedStatement stmt;
try {
stmt = conn.preparestatement (sql);
ResultSet rs = stmt.executequery (SQL);
ResultSetMetaData data = Rs.getmetadata ();
for (int i = 1; I <= data.getcolumncount (); i++) {
Get the number of all columns and the actual number of columns
int columnCount = Data.getcolumncount ();
Gets the column name of the specified column
String columnName = Data.getcolumnname (i);
Gets the column value for the specified column
int columntype = Data.getcolumntype (i);
Gets the data type name of the specified column
String columntypename = Data.getcolumntypename (i);
The name of the catalog where
String catalogname = Data.getcatalogname (i);
Classes that correspond to data types
String columnclassname = Data.getcolumnclassname (i);
Maximum number of characters in a database type
int columndisplaysize = Data.getcolumndisplaysize (i);
The title of the default column
String ColumnLabel = Data.getcolumnlabel (i);
Get the schema of the column
String schemaName = Data.getschemaname (i);
Accuracy of a column type (length of type)
int precision = data.getprecision (i);
Number of digits after the decimal point
int scale = Data.getscale (i);
Get the table name for a column
String tableName = Data.gettablename (i);
Whether to increment automatically
Boolean isautoinctement = Data.isautoincrement (i);
Whether it is a currency type in the database
Boolean iscurrency = Data.iscurrency (i);
is empty
int isnullable = data.isnullable (i);
is read-only
Boolean isreadonly = Data.isreadonly (i);
Can appear in the Where
Boolean issearchable = Data.issearchable (i);
System.out.println (ColumnCount);
System.out.println ("Get column" + i + "field name:" + columnName);
System.out.println ("Get column" + i + "type, return the number in the SqlType:" + ColumnType);
System.out.println ("Get column" + i + "Data type name:" + columntypename);
System.out.println ("Get column" + i + "Location of the Catalog name:" + catalogname);
System.out.println ("Get column" + i + "corresponding data type class:" + Columnclassname);
System.out.println ("Get column" + i + "maximum number of characters in the database type:" + columndisplaysize);
System.out.println ("Get column" + i + "The title of the default column:" + ColumnLabel);
System.out.println ("Get column" + i + "mode:" + schemaName);
System.out.println ("Get column" + i + "type of accuracy (length of type):" + precision);
System.out.println ("Get column" + i + "number of digits after decimal point:" + scale);
System.out.println ("Get column" + i + "corresponding table name:" + tableName);
System.out.println ("Get column" + i + "is automatically incremented:" + isautoinctement);
System.out.println ("Get column" + i + "in the database is currency type:" + iscurrency);
System.out.println ("Get column" + i + "is empty:" + isnullable);
System.out.println ("Get column" + i + "is read-only:" + isreadonly);
System.out.println ("Get column" + i + "can appear in Where:" + issearchable);
}
} catch (SQLException e) {
E.printstacktrace ();
}
}
}


In practice, you can also use case clauses to handle different types of fields:

Switch (ColumnType) {
Case Types.NUMERIC:classFactory.setprop (Entity, ColumnName, Rs.getlong (i));
Break
Case Types.VARCHAR:classFactory.setprop (Entity, ColumnName, rs.getstring (i));
Break
Case Types.DATE:classFactory.setprop (Entity, ColumnName, rs.getdate (i));
Break
Case Types.TIMESTAMP:classFactory.setprop (Entity, ColumnName, Rs.gettimestamp (i));
Break
Case Types.TIME:classFactory.setprop (Entity, ColumnName, Rs.gettime (i));
Break
Case Types.BOOLEAN:classFactory.setprop (Entity, ColumnName, Rs.getboolean (i));
Break
Case Types.ARRAY:classFactory.setprop (Entity, ColumnName, Rs.getarray (i));
Break
Case Types.BIGINT:classFactory.setprop (Entity, ColumnName, Rs.getint (i));
Break
Case Types.BINARY:classFactory.setprop (Entity, ColumnName, Rs.getbinarystream (i));
Break
Case Types.BLOB:classFactory.setprop (Entity, ColumnName, Rs.getblob (i));
Break
Case Types.CHAR:classFactory.setprop (Entity, ColumnName, rs.getstring (i));
Break
Case Types.INTEGER:classFactory.setprop (Entity, ColumnName, Rs.getint (i));
Break
Case Types.DOUBLE:classFactory.setprop (Entity, columnname,rs.getdouble (i));
Break
Case Types.FLOAT:classFactory.setprop (Entity, ColumnName, rs.getfloat (i));
Break
Case Types.SMALLINT:classFactory.setprop (Entity, ColumnName, Rs.getint (i));
Break
Case Types.DECIMAL:classFactory.setprop (Entity, ColumnName, Rs.getlong (i));
Break
Default:classFactory.setprop (Entity, ColumnName, Rs.getobject (i));
Break
}

How Java obtains the fields and field types of a database