JDBC读取数据库元数据,生成JAVA实体类

最新推荐文章于 2021-12-30 09:30:03 发布

转载最新推荐文章于 2021-12-30 09:30:03 发布 · 5.4k 阅读

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#数据库 #jdbc #java #string #import #image

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本文介绍了一种利用JDBC从数据库元数据中自动生成JAVA实体类的方法。该方法通过获取指定表的所有列及其类型，并根据这些信息生成对应的实体类代码，包括属性及getter和setter方法。

JDBC读取数据库元数据,生成JAVA实体类 package com.nffish.util; import java.io.FileWriter; import java.io.IOException; import java.io.PrintWriter; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSetMetaData; import java.sql.SQLException; import com.nffish.common.DBSession; public class GenEntityTool { private String tablename = "petDiary"; 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.* public GenEntityTool() { Connection conn = DBSession.getConnection(); // 得到数据库连接 String strsql = "select * from " + tablename; try { PreparedStatement pstmt = conn.prepareStatement(strsql); ResultSetMetaData rsmd = pstmt.getMetaData(); int size = rsmd.getColumnCount(); // 共有多少列 colnames = new String[size]; colTypes = new String[size]; colSizes = new int[size]; for (int i = 0; i < rsmd.getColumnCount(); i++) { colnames[i] = rsmd.getColumnName(i + 1); colTypes[i] = rsmd.getColumnTypeName(i + 1); if (colTypes[i].equalsIgnoreCase("datetime")) { f_util = true; } if (colTypes[i].equalsIgnoreCase("image") || colTypes[i].equalsIgnoreCase("text")) { f_sql = true; } colSizes[i] = rsmd.getColumnDisplaySize(i + 1); } String content = parse(colnames, colTypes, colSizes); try { FileWriter fw = new FileWriter(initcap(tablename) + ".java"); PrintWriter pw = new PrintWriter(fw); pw.println(content); pw.flush(); pw.close(); } catch (IOException e) { e.printStackTrace(); } } catch (SQLException e) { e.printStackTrace(); } finally { DBSession.closeConnection(conn); } } /** * 解析处理(生成实体类主体代码) */ private String parse(String[] colNames, String[] colTypes, int[] colSizes) { StringBuffer sb = new StringBuffer(); if (f_util) { sb.append("import java.util.Date;/r/n"); } if (f_sql) { sb.append("import java.sql.*;/r/n/r/n/r/n"); } sb.append("public class " + initcap(tablename) + " {/r/n"); processAllAttrs(sb); processAllMethod(sb); sb.append("}/r/n"); System.out.println(sb.toString()); return sb.toString(); } /** * 生成所有的方法 * * @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("/t/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"); } } /** * 解析输出属性 * * @return */ private void processAllAttrs(StringBuffer sb) { for (int i = 0; i < colnames.length; i++) { sb.append("/tprivate " + sqlType2JavaType(colTypes[i]) + " " + colnames[i] + ";/r/n"); } } /** * 把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); } private String sqlType2JavaType(String sqlType) { if (sqlType.equalsIgnoreCase("bit")) { return "bool"; } else if (sqlType.equalsIgnoreCase("tinyint")) { return "byte"; } else if (sqlType.equalsIgnoreCase("smallint")) { return "short"; } else if (sqlType.equalsIgnoreCase("int")) { return "int"; } else if (sqlType.equalsIgnoreCase("bigint")) { return "long"; } else if (sqlType.equalsIgnoreCase("float")) { return "float"; } else if (sqlType.equalsIgnoreCase("decimal") || sqlType.equalsIgnoreCase("numeric") || sqlType.equalsIgnoreCase("real")) { return "double"; } else if (sqlType.equalsIgnoreCase("money") || sqlType.equalsIgnoreCase("smallmoney")) { return "double"; } else if (sqlType.equalsIgnoreCase("varchar") || sqlType.equalsIgnoreCase("char") || sqlType.equalsIgnoreCase("nvarchar") || sqlType.equalsIgnoreCase("nchar")) { return "String"; } else if (sqlType.equalsIgnoreCase("datetime")) { return "Date"; } else if (sqlType.equalsIgnoreCase("image")) { return "Blob"; } else if (sqlType.equalsIgnoreCase("text")) { return "Clob"; } return null; } public static void main(String[] args) { new GenEntityTool(); } }