Java DatabaseMetaData getTypeInfo()方法与示例

2024-05-09 00:52:06 307

getTypeInfo()的DatabaseMetaData接口的方法用于获得由底层数据库支持的所有数据类型的说明。

此方法返回一个ResultSet对象，该对象描述了受支持的数据类型。该对象保存以下详细信息的值（作为列名）-

栏名
数据类型
描述
TYPE_NAME
串
数据类型的名称。
数据类型
整型
表示此数据类型的整数值。
精确
整型
此数据类型的最大精度。
LITERAL_PREFIX
串
前缀用于引用字符串文字。
LITERAL_SUFFIX
串
后缀用于引用字符串文字。
区分大小写
布尔值
确定此数据类型是否区分大小写
UNSIGNED_ATTRIBUTE
布尔值
确定此数据类型是否为未签名的属性。
FIXED_PREC_SCALE
布尔值
确定当前数据类型是否可以用作货币值。
自动递增
布尔值
确定当前数据类型是否可用于自动增量。
LOCAL_TYPE_NAME
串
此数据类型的本地化版本。

获取DatabaseMetaData对象-

确保您的数据库已启动并正在运行。

使用registerDriver()DriverManager类的方法注册驱动程序。传递与基础数据库相对应的驱动程序类的对象。

使用getConnection()DriverManager类的方法获取连接对象。将URL和数据库中的用户密码作为字符串变量传递给数据库。

使用getMetaData()Connection接口的方法获取有关当前连接的DatabaseMetaData对象。

最后，通过调用getTypeInfo()DatabaseMetaData接口的方法来获取ResultSet对象，其中包含受支持的数据类型的描述。

下面的JDBC程序建立与MySQL数据库的连接，检索所有数据类型的描述。

示例

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
public class DatabaseMetadata_getTypeInfo {
   public static void main(String args[]) throws SQLException {
      //注册驱动程序
      DriverManager.registerDriver(new com.mysql.jdbc.Driver());
      //获得连接
      String url = "jdbc:mysql://localhost/mydatabase";
      Connection con = DriverManager.getConnection(url, "root", "password");
      System.out.println("Connection established......");
      //检索元数据对象
      DatabaseMetaData metaData = con.getMetaData();
      //检索数据库中的列
      ResultSet info = metaData.getTypeInfo();
      //打印列名称和大小
      while (info.next()) {
         System.out.println("Data type name: "+info.getString("TYPE_NAME"));
         System.out.println("Integer value representing this datatype: "+info.getInt("DATA_TYPE"));
         System.out.println("Maximum precision of this datatype: "+info.getInt("PRECISION"));
         if(info.getBoolean("CASE_SENSITIVE")) {
            System.out.println("Current datatype is case sensitive ");
         } else {
            System.out.println("Current datatype is not case sensitive ");
         }
         if(info.getBoolean("AUTO_INCREMENT")) {
            System.out.println("Current datatype can be used for auto increment");
         } else {
            System.out.println("Current datatype can not be used for auto increment");
         }
         System.out.println(" ");
      }
   }
}

输出结果

Connection established......
Data type name: BIT
Integer value representing this datatype: -7
Maximum precision of this datatype: 1
Current datatype is case sensitive
Current datatype can not be used for auto increment
Data type name: BOOL
Integer value representing this datatype: -7
Maximum precision of this datatype: 1
Current datatype is case sensitive
Current datatype can not be used for auto increment
Data type name: TINYINT
Integer value representing this datatype: -6
Maximum precision of this datatype: 3
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: TINYINT UNSIGNED
Integer value representing this datatype: -6
Maximum precision of this datatype: 3
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: BIGINT
Integer value representing this datatype: -5
Maximum precision of this datatype: 19
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: BIGINT UNSIGNED
Integer value representing this datatype: -5
Maximum precision of this datatype: 20
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: LONG VARBINARY
Integer value representing this datatype: -4
Maximum precision of this datatype: 16777215
Current datatype is case sensitive
Current datatype can not be used for auto increment
Data type name: MEDIUMBLOB
Integer value representing this datatype: -4
Maximum precision of this datatype: 16777215
Current datatype is case sensitive
Current datatype can not be used for auto increment
Data type name: LONGBLOB
Integer value representing this datatype: -4
Maximum precision of this datatype: 2147483647
Current datatype is case sensitive
Current datatype can not be used for auto increment
Data type name: BLOB
Integer value representing this datatype: -4
Maximum precision of this datatype: 65535
Current datatype is case sensitive
Current datatype can not be used for auto increment
Data type name: TINYBLOB
Integer value representing this datatype: -4
Maximum precision of this datatype: 255
Current datatype is case sensitive
Current datatype can not be used for auto increment
Data type name: VARBINARY
Integer value representing this datatype: -3
Maximum precision of this datatype: 255
Current datatype is case sensitive
Current datatype can not be used for auto increment
Data type name: BINARY
Integer value representing this datatype: -2
Maximum precision of this datatype: 255
Current datatype is case sensitive
Current datatype can not be used for auto increment
Data type name: LONG VARCHAR
Integer value representing this datatype: -1
Maximum precision of this datatype: 16777215
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: MEDIUMTEXT
Integer value representing this datatype: -1
Maximum precision of this datatype: 16777215
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: LONGTEXT
Integer value representing this datatype: -1
Maximum precision of this datatype: 2147483647
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: TEXT
Integer value representing this datatype: -1
Maximum precision of this datatype: 65535
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: TINYTEXT
Integer value representing this datatype: -1
Maximum precision of this datatype: 255
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: CHAR
Integer value representing this datatype: 1
Maximum precision of this datatype: 255
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: NUMERIC
Integer value representing this datatype: 2
Maximum precision of this datatype: 65
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: DECIMAL
Integer value representing this datatype: 3
Maximum precision of this datatype: 65
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: INTEGER
Integer value representing this datatype: 4
Maximum precision of this datatype: 10
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: INTEGER UNSIGNED
Integer value representing this datatype: 4
Maximum precision of this datatype: 10
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: INT
Integer value representing this datatype: 4
Maximum precision of this datatype: 10
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: INT UNSIGNED
Integer value representing this datatype: 4
Maximum precision of this datatype: 10
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: MEDIUMINT
Integer value representing this datatype: 4
Maximum precision of this datatype: 7
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: MEDIUMINT UNSIGNED
Integer value representing this datatype: 4
Maximum precision of this datatype: 8
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: SMALLINT
Integer value representing this datatype: 5
Maximum precision of this datatype: 5
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: SMALLINT UNSIGNED
Integer value representing this datatype: 5
Maximum precision of this datatype: 5
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: FLOAT
Integer value representing this datatype: 7
Maximum precision of this datatype: 10
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: DOUBLE
Integer value representing this datatype: 8
Maximum precision of this datatype: 17
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: DOUBLE PRECISION
Integer value representing this datatype: 8
Maximum precision of this datatype: 17
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: REAL
Integer value representing this datatype: 8
Maximum precision of this datatype: 17
Current datatype is not case sensitive
Current datatype can be used for auto increment
Data type name: VARCHAR
Integer value representing this datatype: 12
Maximum precision of this datatype: 255
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: ENUM
Integer value representing this datatype: 12
Maximum precision of this datatype: 65535
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: SET
Integer value representing this datatype: 12
Maximum precision of this datatype: 64
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: DATE
Integer value representing this datatype: 91
Maximum precision of this datatype: 0
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: TIME
Integer value representing this datatype: 92
Maximum precision of this datatype: 0
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: DATETIME
Integer value representing this datatype: 93
Maximum precision of this datatype: 0
Current datatype is not case sensitive
Current datatype can not be used for auto increment
Data type name: TIMESTAMP
Integer value representing this datatype: 93
Maximum precision of this datatype: 0
Current datatype is not case sensitive
Current datatype can not be used for auto increment

Java DatabaseMetaData getTypeInfo()方法与示例

示例

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