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使用Java实现Oracle表结构转换为PostgreSQL的示例方案(AI)

article 2025/3/21 4:43:52

核心代码

import java.sql.*;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class OracleToPGConverter {
    // 类型映射表
    private static final Map<String, String> TYPE_MAPPING = new HashMap<>();
    static {
        TYPE_MAPPING.put("VARCHAR2", "VARCHAR");
        TYPE_MAPPING.put("NUMBER", "NUMERIC");
        TYPE_MAPPING.put("DATE", "TIMESTAMP");
        TYPE_MAPPING.put("CLOB", "TEXT");
        TYPE_MAPPING.put("BLOB", "BYTEA");
    }

    public static void main(String[] args) {
        String oracleTable = "EMPLOYEES";
        
        try {
            // 1. 连接Oracle数据库
            Connection oracleConn = DriverManager.getConnection(
                "jdbc:oracle:thin:@host:port:sid", "user", "password");
            
            // 2. 获取表结构元数据
            TableMetaData tableMeta = extractMetaData(oracleConn, oracleTable);
            
            // 3. 生成PG DDL
            String pgDDL = generatePGDDL(tableMeta);
            
            // 4. 连接PostgreSQL执行
            Connection pgConn = DriverManager.getConnection(
                "jdbc:postgresql://host:port/dbname", "user", "password");
            
            executeDDL(pgConn, pgDDL);
            
            // 关闭连接
            oracleConn.close();
            pgConn.close();
            
            System.out.println("转换完成！");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 提取Oracle元数据
    private static TableMetaData extractMetaData(Connection conn, String tableName) throws SQLException {
        TableMetaData meta = new TableMetaData();
        meta.tableName = tableName.toLowerCase(); // PG默认小写
        
        // 获取列信息
        try (Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery(
                 "SELECT column_name, data_type, data_length, data_precision, data_scale, nullable " +
                 "FROM all_tab_columns WHERE table_name = '" + tableName + "'")) {
            while (rs.next()) {
                Column col = new Column();
                col.name = rs.getString("column_name").toLowerCase();
                col.type = rs.getString("data_type");
                col.length = rs.getInt("data_length");
                col.precision = rs.getInt("data_precision");
                col.scale = rs.getInt("data_scale");
                col.nullable = "Y".equals(rs.getString("nullable"));
                meta.columns.add(col);
            }
        }
        
        // 获取主键信息
        try (Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery(
                 "SELECT column_name FROM all_cons_columns " +
                 "WHERE constraint_name = ( " +
                 "  SELECT constraint_name FROM all_constraints " +
                 "  WHERE table_name = '" + tableName + "' AND constraint_type = 'P'))")) {
            while (rs.next()) {
                meta.primaryKeys.add(rs.getString("column_name").toLowerCase());
            }
        }
        
        return meta;
    }

    // 生成PostgreSQL DDL
    private static String generatePGDDL(TableMetaData meta) {
        StringBuilder ddl = new StringBuilder();
        ddl.append("CREATE TABLE ").append(meta.tableName).append(" (\n");
        
        List<String> columnDefs = new ArrayList<>();
        for (Column col : meta.columns) {
            String def = "  " + col.name + " " + mapDataType(col);
            if (!col.nullable) def += " NOT NULL";
            columnDefs.add(def);
        }
        
        if (!meta.primaryKeys.isEmpty()) {
            columnDefs.add("  PRIMARY KEY (" + String.join(", ", meta.primaryKeys) + ")");
        }
        
        ddl.append(String.join(",\n", columnDefs));
        ddl.append("\n);");
        return ddl.toString();
    }

    // 数据类型转换
    private static String mapDataType(Column col) {
        String mappedType = TYPE_MAPPING.getOrDefault(col.type, "TEXT");
        
        if ("NUMBER".equals(col.type)) {
            if (col.scale > 0) {
                return "NUMERIC(" + col.precision + "," + col.scale + ")";
            } else if (col.precision > 0) {
                return "NUMERIC(" + col.precision + ")";
            }
            return "NUMERIC";
        }
        
        if ("VARCHAR2".equals(col.type)) {
            return "VARCHAR(" + (col.length > 0 ? col.length : 255) + ")";
        }
        
        return mappedType;
    }

    // 执行DDL
    private static void executeDDL(Connection conn, String ddl) throws SQLException {
        try (Statement stmt = conn.createStatement()) {
            stmt.executeUpdate(ddl);
        }
    }

    // 元数据存储类
    static class TableMetaData {
        String tableName;
        List<Column> columns = new ArrayList<>();
        List<String> primaryKeys = new ArrayList<>();
    }

    // 列定义类
    static class Column {
        String name;
        String type;
        int length;
        int precision;
        int scale;
        boolean nullable;
    }
}

使用说明

‌1.配置数据库连接‌

修改Oracle连接字符串（jdbc:oracle:thin:@host:port）
修改PostgreSQL连接字符串（jdbc:postgresql://host/dbname）
填写正确的用户名密码

2.功能扩展建议

// 添加索引转换（示例）
private static void extractIndexes(Connection conn, TableMetaData meta) throws SQLException {
    try (Statement stmt = conn.createStatement();
         ResultSet rs = stmt.executeQuery(
             "SELECT index_name, column_name " +
             "FROM all_ind_columns " +
             "WHERE table_name = '" + meta.tableName.toUpperCase() + "'")) {
        while (rs.next()) {
            String indexName = rs.getString("index_name");
            String column = rs.getString("column_name").toLowerCase();
            // 处理索引元数据...
        }
    }
}

// 处理自增序列（Oracle序列转PG SERIAL）
private static String handleAutoIncrement() {
    // Oracle: 使用触发器+序列
    // PostgreSQL: 使用SERIAL类型或GENERATED ALWAYS AS IDENTITY
    return "SERIAL";
}

// 添加注释支持
private static void addColumnComments() {
    // 从Oracle的ALL_COL_COMMENTS获取注释
    // 生成PostgreSQL的COMMENT语句
}

‌3.‌运行注意事项‌

需要JDBC驱动：
- Oracle: ojdbc8.jar
- PostgreSQL: postgresql-42.x.jar
权限要求：
- Oracle用户需要访问ALL_TAB_COLUMNS等系统视图
- PG用户需要有建表权限
命名规范：
- 强制转换为小写（PostgreSQL默认小写）
- 特殊字符需用引号处理

‌4.数据类型映射扩展

// 更完整的类型映射建议
TYPE_MAPPING.put("NVARCHAR2", "VARCHAR");
TYPE_MAPPING.put("RAW", "BYTEA");
TYPE_MAPPING.put("TIMESTAMP(6)", "TIMESTAMP");
TYPE_MAPPING.put("FLOAT", "DOUBLE PRECISION");