Java代码实体类生成SQL语句（Java实体类转数据库）

package Main;

import javax.xml.bind.annotation.XmlElement;
import java.io.*;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;

public class GenerateSqlFromEntityUtil { 
   

	public static void main(String[] a) { 
   
		// 实体类的位置
		Class klass = cn.ac.azure.model.User.class;
		// 生成的sql语句的位置
		String outputPath = "D:/outSql/User.txt";
		generateTableSql(klass, outputPath, null);
		System.out.println("生成结束");
	}

	public static void writeFile(String content, String outputPath) { 
   
		File file = new File(outputPath);
		System.out.println("文件路径: " + file.getAbsolutePath());
		// 输出文件的路径
		if (!file.getParentFile().exists()) { 
   
			file.getParentFile().mkdirs();
		}
		FileOutputStream fos = null;
		OutputStreamWriter osw = null;
		BufferedWriter out = null;

		try { 
   
			// 如果文件存在，就删除
			if (file.exists()) { 
   
				file.delete();
			}
			file.createNewFile();
			fos = new FileOutputStream(file, true);
			osw = new OutputStreamWriter(fos);
			out = new BufferedWriter(osw);
			out.write(content);
			// 清空缓冲流，把缓冲流里的文本数据写入到目标文件里
			out.flush();
		} catch (FileNotFoundException e) { 
   
			e.printStackTrace();
		} catch (IOException e) { 
   
			e.printStackTrace();
		} finally { 
   
			try { 
   
				fos.close();
			} catch (IOException e) { 
   
				e.printStackTrace();
			}

			try { 
   
				osw.close();
			} catch (IOException e) { 
   
				e.printStackTrace();
			}

			try { 
   
				out.close();
			} catch (IOException e) { 
   
				e.printStackTrace();
			}
		}
	}

	public static void generateTableSql(Class obj, String outputPath, String tableName) { 
   
		// tableName 如果是 null，就用类名做表名
		if (tableName == null || tableName.equals("")) { 
   
			tableName = obj.getName();
			tableName = tableName.substring(tableName.lastIndexOf(".") + 1);
		}
		// 表名用大写字母
		tableName = tableName.toUpperCase();

		Field[] fields = obj.getDeclaredFields();
		Object param;
		String column;

		StringBuilder sb = new StringBuilder();

		sb.append("drop table if exists ").append(tableName).append(";\r\n");

		sb.append("\r\n");

		sb.append("create table ").append(tableName).append("(\r\n");

		System.out.println(tableName);

		boolean firstId = true;

		for (int i = 0; i < fields.length; i++) { 
   
			Field f = fields[i];

			column = f.getName();

			System.out.println(column + ", " + f.getType().getSimpleName());

			param = f.getType();
			sb.append(column); // 一般第一个是主键

			if (param instanceof Integer) { 
   
				sb.append(" INTEGER ");
			} else { 
   
				// 注意：根据需要，自行修改 varchar 的长度。这里设定为长度等于 50
				int length = 50;
				sb.append(" VARCHAR(" + length + ")");
			}

			if (firstId == true) { 
   
				sb.append(" PRIMARY KEY ");
				firstId = false;
			}

			// 获取字段中包含 fieldMeta 的注解

			// 获取属性的所有注释
			Annotation[] allAnnotations = f.getAnnotations();

			XmlElement xmlElement = null;
			Class annotationType = null;

			for (Annotation an : allAnnotations) { 
   
				sb.append(" COMMIT '");
				xmlElement = (XmlElement) an;
				annotationType = an.annotationType();
				param = ((XmlElement) an).name();
				System.out.println("属性 " + f.getName() + " ----- 的注释类型有: " + param);
				sb.append(param).append("'");
			}

			if (i != fields.length - 1) { 
    // 最后一个属性后面不加逗号
				sb.append(", ");
			}

			sb.append("\n");
		}

		String sql = sb.toString();

		sql = sb.substring(0, sql.length() - 1) + "\n) " + "ENGINE = INNODB DEFAULT CHARSET = utf8;";

		writeFile(sql, outputPath);
	}
}