java 从数据库表反射出实体类，自动生成实体类

package com.soft.ms.test;

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.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Date;

/**
 * 根据数据库表结构生成相应的JavaBean 
 * 
 * 思路 
 * 1、创建数据库连接 
 * 2、获取数据库表、表注释 
 * 3、获取数据库表中字段名、字段类型、字段注释
 * 4、构建StringBuffer缓存 
 * 5、写入文件 
 * 6、关闭连接、输入流等等
 * 
 * @author ella_li
 * 
 */
public class GenEntityOracle {
	private String packageOutPath = "com.soft.ms.test";// 指定实体生成所在包的路径
	private String authorName = "ella_li";// 作者名字
	private String[] tableNames;
	private String[] tablePre = { "TB_" };
	private String[] colsPre = { "F_NB_", "F_VC_", "F_CR_", "F_DT_"};
	private String[] colnames; // 列名数组
	private String[] colTypes; // 列名类型数组
	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.*

	// 数据库连接
	private static final String URL = "jdbc:oracle:thin:@192.168.0.114:1521:oracle";
	private static final String NAME = "ms";
	private static final String PASS = "ms";
	private static final String DRIVER = "oracle.jdbc.driver.OracleDriver";
	private Connection con = null;
	private Statement pStemt = null;
	private ResultSet rs = null;
	private ResultSetMetaData rsmd = null;

	public GenEntityOracle() {
		connect();
		getAllTables();
	}

	/**
	 * 1、创建数据库连接
	 */
	private void connect() {
		try {
			Class.forName(DRIVER);
			con = DriverManager.getConnection(URL, NAME, PASS);
			pStemt = (Statement) con.createStatement();
		} catch (ClassNotFoundException | SQLException e) {
			e.printStackTrace();
		}
	}

	private void colseConnect() {
		try {
			if (con != null) {
				con.close();
				con = null;
			}
			if (pStemt != null) {
				pStemt.close();
				pStemt = null;
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}

	}

	/**
	 * 获取所有表名
	 */
	private void getAllTables() {
		String sql = "SELECT TABLE_NAME FROM USER_TABLES";
		try {
			rs = pStemt.executeQuery(sql);
			String s = "";
			while (rs.next()) {
				s = s + rs.getString("TABLE_NAME") + ",";
			}
			tableNames = s.substring(0,s.length()-1).split(",");
			for (String tableName : tableNames) {
				getTableInfo(tableName);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			colseConnect();
		}
	}

	/**
	 * 获取单个数据库表信息
	 */
	private void getTableInfo(String tableName) {
		int size = 0;
		String sql = "SELECT * FROM " + tableName;
		try {
			rs = pStemt.executeQuery(sql);
			rsmd = rs.getMetaData();
			size = rsmd.getColumnCount();
			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);

				if (colTypes[i].equalsIgnoreCase("date")
						|| colTypes[i].equalsIgnoreCase("timestamp")) {
					f_util = true;
				}
				if (colTypes[i].equalsIgnoreCase("blob")
						|| colTypes[i].equalsIgnoreCase("char")) {
					f_sql = true;
				}
				colSizes[i] = rsmd.getColumnDisplaySize(i + 1);
			}
			//规范化表名
			String normTableName = normTableName(tableName);
			//获取单张数据库表注释
			String tableComment = getTableComment(tableName);
			//获取单张数据库表的所有列信息
			StringBuffer tempSb = getColsInfo(tableName);
			//生成JavaBean文件
			genFile(normTableName, getSb(normTableName, tableComment, tempSb));
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

	/**
	 * 规范类名
	 * 
	 * @param tableName
	 * @return
	 */
	public String normTableName(String tableName) {
		String result = "";
		for (String temp : tablePre) {
			int index = tableName.indexOf(temp);
			if (index >= 0) {
				tableName = tableName.substring(index + temp.length());
				String[] names = tableName.split("_");
				if (null != names && names.length > 0) {
					for (String name : names) {
						result += captureName(name.toLowerCase());
					}
				}
			}
		}
		return result;
	}

	/**
	 * 获取单张数据库表注释
	 * 
	 * @param tableName
	 * @return
	 */
	private String getTableComment(String tableName) {
		String str = "";
		String sql = "select * from user_tab_comments where table_name = '"
				+ tableName + "'";
		try {
			rs = pStemt.executeQuery(sql);
			while (rs.next()) {
				str = rs.getString("comments");
				if (null != str && str.indexOf("
") != -1) {
					str = str.replace("
", "");
				}
				if (null != str && str.indexOf("
") != -1) {
					str = str.replace("
", "");
				}
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return str;
	}

	/**
	 * 获取单张数据库表的所有列信息
	 * 
	 * @param tableName
	 */
	private StringBuffer getColsInfo(String tableName) {
		StringBuffer temp = new StringBuffer();
		for (int i = 0; i < colnames.length; i++) {
			temp.append("	private " + getColsType(colTypes[i]) + " "
					+ getColsName(colnames[i]) + ";   //"
					+ getColComment(tableName, colnames[i]) + "
");
			String colname = getColsName(colnames[i]);
			String colnameUp = captureName(colname);
			temp.append("
	public void set" + colnameUp + "("
					+ getColsType(colTypes[i]) + " " + colname + "){
");
			temp.append("		this." + colname + "=" + colname + ";
");
			temp.append("	}
");
			temp.append("
	public " + getColsType(colTypes[i]) + " get"
					+ colnameUp + "(){
");
			temp.append("		return " + colname + ";
");
			temp.append("	}
");
		}
		return temp;
	}

	/**
	 * 获取列类型
	 * 
	 * @param sqlType
	 * @return
	 */
	private String getColsType(String sqlType) {
		if (sqlType.equalsIgnoreCase("binary_double")) {
			return "double";
		} else if (sqlType.equalsIgnoreCase("binary_float")) {
			return "float";
		} else if (sqlType.equalsIgnoreCase("blob")) {
			return "byte[]";
		} else if (sqlType.equalsIgnoreCase("blob")) {
			return "byte[]";
		} else if (sqlType.equalsIgnoreCase("char")
				|| sqlType.equalsIgnoreCase("nvarchar2")
				|| sqlType.equalsIgnoreCase("varchar2")) {
			return "String";
		} else if (sqlType.equalsIgnoreCase("date")
				|| sqlType.equalsIgnoreCase("timestamp")
				|| sqlType.equalsIgnoreCase("timestamp with local time zone")
				|| sqlType.equalsIgnoreCase("timestamp with time zone")) {
			return "Date";
		} else if (sqlType.equalsIgnoreCase("number")) {
			return "Long";
		}
		return "String";
	}

	/**
	 * 获取列名
	 * 
	 * @param str
	 * @return
	 */
	private String getColsName(String str) {
		for (String temp : colsPre) {
			int preIndex = str.indexOf(temp);
			if (preIndex >= 0) {
				str = str.substring(preIndex + temp.length());
				str = str.replace("_", "").toLowerCase();
			}
		}
		return str;
	}

	/**
	 * 获取列注释
	 * 
	 * @param tableName
	 * @param columnName
	 * @return
	 */
	private String getColComment(String tableName, String columnName) {
		String str = "";
		String sql = "select comments from USER_COL_COMMENTS where table_name= '"
				+ tableName + "' and column_name= '" + columnName + "'";
		try {
			rs = pStemt.executeQuery(sql);
			while (rs.next()) {
				str = rs.getString("comments");
				if (null != str && str.indexOf("
") != -1) {
					str = str.replace("
", "");
				}
				if (null != str && str.indexOf("
") != -1) {
					str = str.replace("
", "");
				}
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return str;
	}

	/**
	 * 构建StringBuffer缓存
	 * 
	 * @param tableName
	 * @param tableComment
	 * @param colSb
	 * @return
	 */
	private StringBuffer getSb(String tableName, String tableComment,
			StringBuffer colSb) {
		StringBuffer sb = new StringBuffer();
		sb.append("package " + this.packageOutPath + ";
");
		// 判断是否导入工具包
		if (f_util) {
			sb.append("import java.util.Date;
");
		}
		if (f_sql) {
			sb.append("import java.sql.*;
");
		}
		sb.append("
");
		// 注释部分
		sb.append("   /**
");
		sb.append("    * " + tableName + " 实体类              " + tableComment + "
");
		sb.append("    * " + new Date() + "
");
		sb.append("    * @author " + this.authorName + "
");
		sb.append("    */ 
");
		// 实体部分
		sb.append("

public class " + tableName + "{
");
		sb.append("	private static final long serialVersionUID = 1L;
");
		sb.append(colSb);
		sb.append("}
");
		return sb;
	}

	/**
	 * 生成JavaBean文件
	 * 
	 * @param content
	 */
	private void genFile(String tableName, StringBuffer content) {
		try {
			File directory = new File("");
			String outputPath = directory.getAbsolutePath() + "/src/"
					+ this.packageOutPath.replace(".", "/") + "/" + tableName
					+ ".java";
			FileWriter fw = new FileWriter(outputPath);
			PrintWriter pw = new PrintWriter(fw);
			pw.println(content);
			pw.flush();
			pw.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
        /**
	 * 首字母大写
	 * @param name
	 * @return
	 */
	public static String captureName(String name) {
		char[] cs = name.toCharArray();
		cs[0] -= 32;
		return String.valueOf(cs);
	}

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

查询数据库里所有表名和字段名的语句
SQL 查询所有表名：
SELECT NAME FROM SYSOBJECTS WHERE TYPE='U'
SELECT * FROM INFORMATION_SCHEMA.TABLES
查询表的所有字段名：
SELECT NAME FROM SYSCOLUMNS WHERE ID=OBJECT_ID(' 表名' )
SELECT * FROM INFORMATION_SCHEMA.TABLES
SELECT * FROM INFORMATION_SCHEMA.VIEWS
SELECT * FROM INFORMATION_SCHEMA.COLUMNS
ORACLE 查看所有表名:
SELECT TABLE_NAME FROM USER_TABLES
ACCESS 查看所有表名：
SELECT NAME FROM MSYSOBJECTS WHERE TYPE=1 AND FLAGS=0
MSYSOBJECTS 是系统对象，默认情况是隐藏的。通过工具、选项、视图、显示、系统对象可以使之显示出来。