java根据数据库自动生成JavaBean或pojo

之前写了根据实体类生成sql语句和根据结果集封装实体类，现在写下根据数据库生成实体类的小工具。

程序和jar包我已经放在我的github上了：https://github.com/Renhongqiang/JavaGeneratingModel

可以根据数据连接 Connection  生成pojo或者Bean，pojo只包含属性和getter、setter方法，Bean实现可序列化接口并添加一个无参构造器。

使用 Connection 的 getMetaData() 方法可以获取包含数据库的所有表信息的 DatabaseMetaData

使用 ResultSet 的 getMetaData() 方法可以获取表的所有字段信息 ResultSetMetaData

 通过对上面DatabaseMetaData与ResultSetMetaData的操作生成java文件，使用了我定义的Table与Colum两个模型

Table.java: https://github.com/Renhongqiang/JavaGeneratingModel/blob/master/src/com/ren/model/Table.java

Colum: https://github.com/Renhongqiang/JavaGeneratingModel/blob/master/src/com/ren/model/Column.java

关于数据库数据类型与java数据类型的转换：

https://blog.csdn.net/qq_35562664/article/details/56012826

https://blog.csdn.net/zs520ct/article/details/78326204

使用实例：

public static void main(String[] args) throws SQLException, ClassNotFoundException { String url = "jdbc:mysql://localhost:3306/databsename?useSSL=false"; String user = "username"; String pass = "password"; Class.forName("com.mysql.jdbc.Driver"); Connection conn = DriverManager.getConnection(url, user, pass); //java文件输出路径 String path = "H:\\pojo"; GetModel getModel = new GetModel(conn); /* 使用： pojo: 包含属性与getter、setter bean: 包含属性与getter、setter与无参构造器，并实现Serializable接口 */ //生成pojo到path //getModel.generatePojo(path); //生成pojo到path，在pojo中添加包信息"package com.ren.model" //getModel.generatePojo(path, "com.ren.model"); //生成Bean到path //getModel.generateBean(path); //生成Bean到path，在Bean中添加包信息"package com.ren.bean" //getModel.generateBean(path, "com.ren.bean"); }

 

代码：

public class GetModel { private Connection connection; private List<Table> tables; public GetModel() { } public GetModel(Connection connection) throws SQLException { this.connection = connection; this.tables = getTableList(); } public Connection getConnection() { return connection; } public void setConnection(Connection connection) { this.connection = connection; } /** * 获取数据库中所有表信息封装到List<Table> tables * @return List<Table> 包含数据库中所有的表 * @throws SQLException */ private List<Table> getTableList() throws SQLException { List<Table> tableList = new ArrayList<>(); DatabaseMetaData dbMetaData = connection.getMetaData(); ResultSet rs = dbMetaData.getTables(null, null, null, new String[] { "TABLE" }); while (rs.next()) { Table table = new Table(); String tableName = rs.getString("TABLE_NAME"); table.setTableName(tableName); table.setDatabaseName(rs.getString("TABLE_CAT")); table.setColumns(getTableColumnList(tableName)); tableList.add(table); } return tableList; } /** * 获取某表的所有column信息封装到List<Column> columnList中 */ private List<Column> getTableColumnList(String tableName) throws SQLException { List<Column> columnList = new ArrayList<>(); String sql = "select * from " + tableName; PreparedStatement stmt; try { stmt = connection.prepareStatement(sql); ResultSet rs = stmt.executeQuery(sql); ResultSetMetaData data = rs.getMetaData(); for (int i = 1; i <= data.getColumnCount(); i++) { Column column = new Column(); // 获得所有列的数目及实际列数 int columnCount = data.getColumnCount(); // 获得指定列的列名 String columnName = data.getColumnName(i); // 获得指定列的数据类型名 String columnTypeName = data.getColumnTypeName(i); // 对应数据类型的类 String columnClassName = data.getColumnClassName(i); // 在数据库中类型的最大字符个数 int columnDisplaySize = data.getColumnDisplaySize(i); // 某列类型的精确度(类型的长度) int precision = data.getPrecision(i); // 小数点后的位数 int scale = data.getScale(i); // 是否自动递增 Boolean isAutoInctement = data.isAutoIncrement(i); // 是否为空 int isNullable = data.isNullable(i); column.setColumnName(columnName); column.setColumnTypeName(columnTypeName); column.setColumnClassName(columnClassName); column.setTableName(tableName); column.setColumnDisplaySize(columnDisplaySize); column.setPrecision(precision); column.setScale(scale); column.setAutoInctement(isAutoInctement); columnList.add(column); } } catch (SQLException e) { e.printStackTrace(); } return columnList; } /** * 为table创建pojo * @param table 表 * @param path 输出路径 */ private static void writeFilePojo(Table table, String path, String packagePath) { String fileName = path + "\\" + upperCase(table.getTableName()) + ".java"; try { FileWriter writer = new FileWriter(fileName); StringBuilder getterSetter = new StringBuilder(); //需要添加包路径 if (!packagePath.equals("0")) { writer.write("package " + packagePath + ";\n\n"); } writer.write("public class " + upperCase(table.getTableName()) + " {\n"); for (Column column : table.getColumns()) { writer.write(" private " + changeType(column.getColumnTypeName()) + " " + column.getColumnName() + "\n"); //getter() getterSetter.append("\n public " + changeType(column.getColumnTypeName()) + " get" + upperCase(column.getColumnName()) + "() {\n"); getterSetter.append(" return " + column.getColumnName() + ";\n"); getterSetter.append(" }\n\n"); //setter() getterSetter.append(" public void set" + upperCase(column.getColumnName()) + "(" + changeType(column.getColumnTypeName()) + " " + column.getColumnName() + ") {\n"); getterSetter.append(" this." + column.getColumnName() + " = " + column.getColumnName() + ";\n"); getterSetter.append(" }\n"); } writer.write(getterSetter.toString()); writer.write("}"); writer.close(); } catch (IOException e) { e.printStackTrace(); } } /** * 为table创建Bean * @param table 表 * @param path 输出路径 */ private static void writeFileBean(Table table, String path, String packagePath) { String fileName = path + "\\" + upperCase(table.getTableName()) + ".java"; try { FileWriter writer = new FileWriter(fileName); StringBuilder getterSetter = new StringBuilder(); //需要添加包路径 if (!packagePath.equals("0")) { writer.write("package " + packagePath + ";\n\n"); } writer.write("import java.io.Serializable;\n\n"); writer.write("public class " + upperCase(table.getTableName()) + " implements Serializable {\n"); for (Column column : table.getColumns()) { writer.write(" private " + changeType(column.getColumnTypeName()) + " " + column.getColumnName() + "\n"); //getter() getterSetter.append("\n public " + changeType(column.getColumnTypeName()) + " get" + upperCase(column.getColumnName()) + "() {\n"); getterSetter.append(" return " + column.getColumnName() + ";\n"); getterSetter.append(" }\n\n"); //setter() getterSetter.append(" public void set" + upperCase(column.getColumnName()) + "(" + changeType(column.getColumnTypeName()) + " " + column.getColumnName() + ") {\n"); getterSetter.append(" this." + column.getColumnName() + " = " + column.getColumnName() + ";\n"); getterSetter.append(" }\n"); } //无参构造器 writer.write("\n public " + upperCase(table.getTableName()) + "() { }\n"); writer.write(getterSetter.toString()); writer.write("}"); writer.close(); } catch (IOException e) { e.printStackTrace(); } } /** * 将 str 首字母大写 * @param str * @return */ private static String upperCase(String str) { return str.substring(0, 1).toUpperCase() + str.substring(1); } /** * 将数据库类型转换为java中合适的类型 * @param typeName * @return */ private static String changeType(String typeName) { switch (typeName) { case "VARCHAR": case "CHAR": case "TEXT": case "TINYTEXT": case "MEDIUMTEXT": case "LONGTEXT": case "ENUM": case "SET": return "String"; case "BLOB": case "BINARY": case "VARBINARY": case "TINYBLOB": case "MEDIUMBLOB": case "LONGBLOB": return "byte[]"; case "INTEGER": case "ID": case "BIGINT": return "Long"; case "TINYINT": case "SMALLINT": case "MEDIUMINT": case "INT": return "Integer"; case "DECIMAL": return "BigDecimal"; case "BIT": return "Boolean"; case "FLOAT": return "Float"; case "DOUBLE": return "Double"; case "DATE": case "YEAR": return "Date"; case "TIME": return "Time"; } return "String"; } /** * 根据tables生成pojo到path * @param path 输出路径 */ public void generatePojo(String path) { for (Table table : tables) { writeFilePojo(table, path, "0"); System.out.println("已创建Pojo: " + path + "\\" + upperCase(table.getTableName()) + ".java"); } } /** * 根据tables生成Bean到path * @param path 输出路径 */ public void generateBean(String path) { for (Table table : tables) { writeFileBean(table, path, "0"); System.out.println("已创建Bean: " + path + "\\" + upperCase(table.getTableName()) + ".java"); } } /** * 根据tables生成pojo到path * @param path 输出路径 * @param packagePath 添加包路径 */ public void generatePojo(String path, String packagePath) { for (Table table : tables) { writeFilePojo(table, path, packagePath); System.out.println("已创建Pojo: " + path + "\\" + upperCase(table.getTableName()) + ".java 包名：" + packagePath); } } /** * 根据tables生成Bean到path * @param path 输出路径 * @param packagePath 添加包路径 */ public void generateBean(String path, String packagePath) { for (Table table : tables) { writeFileBean(table, path, packagePath); System.out.println("已创建Bean: " + path + "\\" + upperCase(table.getTableName()) + ".java 包名：" + packagePath); } } }