利用JAVA反射，读取数据库表名，自动生成对应实体类

本代码是利用java反射，读取数据库表自动根据表名生成实体类，数据库采用老牌SQLSERVER 2000，驱动为JTDS，其他数据库可根据情况自定修改。

代码中包含了大部分数据库类型与JAVA类型的转换，少数未包含进去的会在生成代码时打印出来，方面后期查找修改。

本文章参考大牛文章，根据自己情况改写，非常感谢大牛提供思路，原文章地址为：https://blog.csdn.net/goodleiwei/article/details/8439023。

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * 从数据库表反射出实体类，自动生成实体类
 * 
 * @author Zero
 *
 */
public class SqlHelper {
	//基本数据配置
	private String packageOutPath = "com.xxx.entity.system";// 指定实体生成所在包的路径
	private String authorName = "Zero";// 作者名字
	private String tablename = "xxx";// 表名
	private String[] colnames; // 列名数组
	private String[] colTypes; // 列名类型数组
	private String version = "V0.01"; // 版本
	private int[] colSizes; // 列名大小数组
	private boolean f_util = false; // 是否需要导入包java.util.*
	private boolean f_sql = false; // 是否需要导入包java.sql.*
	private boolean f_lang = false; // 是否需要导入包java.sql.*
	private String defaultPath = "/src/main/java/";
	// 数据库连接
	private static final String URL = "jdbc:jtds:sqlserver://192.168.29.128:1433/xxx";
	private static final String NAME = "sa";
	private static final String PASS = "xxx";
	private static final String DRIVER = "net.sourceforge.jtds.jdbc.Driver";

	/*
	 * 构造函数
	 */
	public SqlHelper() {
		// 创建连接
		Connection con;
		// 查要生成实体类的表
		String sql = "select * from " + tablename;
		PreparedStatement pStemt = null;
		try {
			try {
				Class.forName(DRIVER);
			} catch (ClassNotFoundException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			}
			con = DriverManager.getConnection(URL, NAME, PASS);
			pStemt = con.prepareStatement(sql);
			ResultSetMetaData rsmd = pStemt.getMetaData();
			int size = rsmd.getColumnCount(); // 统计列
			colnames = new String[size];
			colTypes = new String[size];
			colSizes = new int[size];
			for (int i = 0; i < size; i++) {

				colnames[i] = rsmd.getColumnName(i + 1);
				colTypes[i] = rsmd.getColumnTypeName(i + 1);
				//自动生成包配置
				
				
				// if (colTypes[i].equalsIgnoreCase("datetime")) {
				// f_util = true;
				// }
				if (colTypes[i].equalsIgnoreCase("image") || colTypes[i].equalsIgnoreCase("text")
						|| colTypes[i].equalsIgnoreCase("datetime") || colTypes[i].equalsIgnoreCase("time")
						|| colTypes[i].equalsIgnoreCase("date") || colTypes[i].equalsIgnoreCase("datetime2")) {
					f_sql = true;
				}
				// if (colTypes[i].equalsIgnoreCase("int")) {
				// f_lang = true;
				// }
				colSizes[i] = rsmd.getColumnDisplaySize(i + 1);
			}

			String content = parse(colnames, colTypes, colSizes);

			try {
				File directory = new File("");
				
				String path = this.getClass().getResource("").getPath();

				System.out.println(path);
				
				String outputPath = directory.getAbsolutePath() + this.defaultPath
						+ this.packageOutPath.replace(".", "/") + "/" + initcap(tablename) + ".java";
				System.out.println("执行完毕，生成路径为："+outputPath);
				FileWriter fw = new FileWriter(outputPath);
				PrintWriter pw = new PrintWriter(fw);
				pw.println(content);
				pw.flush();
				pw.close();
			} catch (IOException e) {
				e.printStackTrace();
			}

		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			
		}
	}

	/**
	 * 功能：生成实体类主体代码
	 * 
	 * @param colnames
	 * @param colTypes
	 * @param colSizes
	 * @return
	 */
	private String parse(String[] colnames, String[] colTypes, int[] colSizes) {
		StringBuffer sb = new StringBuffer();
		// 生成package包路径
		sb.append("package " + this.packageOutPath + ";\r\n");
		// 判断是否导入工具包
		if (f_util) {
			sb.append("import java.util.Date;\r\n");
		}
		if (f_sql) {
			sb.append("import java.sql.*;\r\n");
		}
		if (f_lang) {
			sb.append("import java.lang.*;\r\n");
		}

		sb.append("\r\n");
		// 注释部分
		sb.append("   /**\r\n");
		sb.append("    * @文件名称：" + this.tablename + ".java\r\n");
		sb.append("    * @创建时间：" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()) + "\r\n");
		sb.append("    * @创  建  人：" + this.authorName + " \r\n");
		sb.append("    * @文件描述：" + tablename + " 实体类\r\n");
		sb.append("    * @文件版本：" + this.version + " \r\n");
		sb.append("    */ \r\n");
		// 实体部分
		sb.append("\r\n\r\npublic class " + initcap(tablename) + "{\r\n");
		processAllAttrs(sb);// 属性
		processAllMethod(sb);// get set方法
		sb.append("}\r\n");

		// System.out.println(sb.toString());
		return sb.toString();
	}

	/**
	 * 功能：生成所有属性
	 * 
	 * @param sb
	 */
	private void processAllAttrs(StringBuffer sb) {

		for (int i = 0; i < colnames.length; i++) {
			sb.append("\tprivate " + sqlType2JavaType(colTypes[i]) + " " + colnames[i] + ";\r\n");
		}

	}

	/**
	 * 功能：生成所有方法
	 * 
	 * @param sb
	 */
	private void processAllMethod(StringBuffer sb) {

		for (int i = 0; i < colnames.length; i++) {
			sb.append("\tpublic void set" + initcap(colnames[i]) + "(" + sqlType2JavaType(colTypes[i]) + " "
					+ colnames[i] + "){\r\n");
			sb.append("\tthis." + colnames[i] + "=" + colnames[i] + ";\r\n");
			sb.append("\t}\r\n");
			sb.append("\tpublic " + sqlType2JavaType(colTypes[i]) + " get" + initcap(colnames[i]) + "(){\r\n");
			sb.append("\t\treturn " + colnames[i] + ";\r\n");
			sb.append("\t}\r\n");
		}

	}

	/**
	 * 功能：将输入字符串的首字母改成大写
	 * 
	 * @param str
	 * @return
	 */
	private String initcap(String str) {

		char[] ch = str.toCharArray();
		if (ch[0] >= 'a' && ch[0] <= 'z') {
			ch[0] = (char) (ch[0] - 32);
		}

		return new String(ch);
	}

	/**
	 * 功能：获得列的数据类型
	 * 
	 * @param sqlType
	 * @return
	 */
	private String sqlType2JavaType(String sqlType) {

		if (sqlType.equalsIgnoreCase("bit")) {
			return "Boolean";
		} else if (sqlType.equalsIgnoreCase("decimal") || sqlType.equalsIgnoreCase("money")
				|| sqlType.equalsIgnoreCase("smallmoney") || sqlType.equalsIgnoreCase("numeric")
				|| sqlType.equalsIgnoreCase("bigint")) {
			return "Long";
		} else if (sqlType.equalsIgnoreCase("float")) {
			return "Double";
		} else if (sqlType.equalsIgnoreCase("int") || sqlType.equalsIgnoreCase("int identity")) {
			return "Integer";
		} else if (sqlType.equalsIgnoreCase("image") || sqlType.equalsIgnoreCase("varbinary(max)")
				|| sqlType.equalsIgnoreCase("varbinary") || sqlType.equalsIgnoreCase("udt")
				|| sqlType.equalsIgnoreCase("timestamp") || sqlType.equalsIgnoreCase("binary")) {
			return "Byte[]";
		} else if (sqlType.equalsIgnoreCase("nchar") || sqlType.equalsIgnoreCase("nvarchar(max)")
				|| sqlType.equalsIgnoreCase("nvarchar") || sqlType.equalsIgnoreCase("nvarchar(ntext)")
				|| sqlType.equalsIgnoreCase("uniqueidentifier") || sqlType.equalsIgnoreCase("xml")
				|| sqlType.equalsIgnoreCase("char") || sqlType.equalsIgnoreCase("varchar(max)")
				|| sqlType.equalsIgnoreCase("text") || sqlType.equalsIgnoreCase("varchar")) {
			return "String";
		} else if (sqlType.equalsIgnoreCase("real")) {
			return "Float";
		} else if (sqlType.equalsIgnoreCase("smallint") || sqlType.equalsIgnoreCase("tinyint")) {
			return "Short";
		} else if (sqlType.equalsIgnoreCase("date") || sqlType.equalsIgnoreCase("datetime")
				|| sqlType.equalsIgnoreCase("time") || sqlType.equalsIgnoreCase("datetime2")) {
			return "Date";
		} else {
			System.out.println("数据类型异常，类型为：" + sqlType);
		}

		return null;
	}

	/**
	 * 出口 TODO
	 * 
	 * @param args
	 */
	public static void main(String[] args) {

		new SqlHelper();

	}
}