hibernate---根据实体类生成数据库表

博客介绍了Java中与数据库表映射相关的注解使用。@Entity的name属性可指明生成数据库表的名字;主键字段上加@id表明是主键,@GeneratedValue指定主键生成策略;@Column的name指明数据库和实体类字段名称,length指明数据库字段长度。

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如下:

import javax.persistence.*;
import java.util.Date;

@Entity (name = "TB_SYS_LOG")
public class SysLog {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "ID_")
    private Integer id;              
    @Column(name = "TITLE_")
    private String title;     
//get/set方法必须提供
//此处省略get/set方法
       
 }

@Entity 中name属性指明生成数据库 表的名字,加载类上

主键字段名上加@id【表明是主键】、@GeneratedValue(strategy = GenerationType.AUTO)【主键生成策略】

@Column(name="XXX",length="XXX"),name指明数据库和实体类字段名称,length指明数据库字段长度

private static void printTableMetaInfo(Session session) { Connection connection = session.connection(); try { DatabaseMetaData metaData = connection.getMetaData(); ResultSet result = metaData.getColumns(null, null, NameOfTable, null); String strInJava = ""; String typeInJava; while (result.next()) { String columnName = result.getString(4); if ("stampTime".equalsIgnoreCase(columnName)) { continue; } int columnType = result.getInt(5); String nameFirstLetterLower = columnName.substring(0, 1).toLowerCase() + columnName.substring(1); switch (columnType) { case Types.VARCHAR: case Types.LONGVARCHAR: case Types.LONGNVARCHAR: case Types.NVARCHAR: case Types.CHAR: typeInJava = "String"; break; case Types.TINYINT: case Types.SMALLINT: case Types.INTEGER: typeInJava = useInteger ? "Integer" : "int"; break; case Types.TIMESTAMP: case Types.BINARY: typeInJava = "Calendar"; break; case Types.DECIMAL: typeInJava = "BigDecimal"; break; case Types.BIGINT: typeInJava = "BigInteger"; break; case Types.LONGVARBINARY: typeInJava = "byte[]"; break; case Types.DATE: typeInJava = "Calendar"; break; default: throw new Exception("Unknown type " + columnType + " and column is " + columnName); } strInJava += " private " + typeInJava + " " + nameFirstLetterLower + ";\n"; // strInHibernate += "\n"; } String str = "import javax.persistence.Entity;\n" + "import javax.persistence.Id;\n" + "import javax.persistence.Table;\n" + "import java.util.Calendar;\n\n"; str += "@Entity\n"; str += "@Table(name=\"$\")\n".replace("$", NameOfTable); str += "public class $ {\n".replace("$", NameOfTable.substring(2)); str += "\n @Id\n"; str += strInJava; str += "}"; System.out.println(str); StringSelection stringSelection = new StringSelection(str); Clipboard clpbrd = Toolkit.getDefaultToolkit().getSystemClipboard(); clpbrd.setContents(stringSelection, null); } catch (Exception e) { e.printStackTrace(); }
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