java实现CSV文件导入与导出功能

接下来我将为您详细讲解如何使用Java实现CSV文件导入与导出功能，以下是完整攻略：

1. 了解CSV文件格式

CSV(Comma-Separated Values)，即逗号分隔符文件，是一种常见的文件格式。每行数据以逗号或其他符号作为分隔符，可以存储多行数据。在CSV文件中，每行数据都代表一条记录，每行的各个字段代表了该记录的相关信息。

2. 导入CSV文件

2.1 读取CSV文件

我们可以使用Java的I/O操作来读取CSV文件中的数据，具体步骤如下：

File file = new File("filename.csv");
BufferedReader reader = new BufferedReader(new FileReader(file));
String line = "";

while((line = reader.readLine()) != null) {
  String[] fields = line.split(",");

  // 处理每一行的数据
}

reader.close();

2.2 将CSV数据导入到数据库

读取CSV文件数据后，我们可以将数据导入到数据库中，常用的数据库可以是MySQL，Oracle等。

String username = "root";
String password = "password";
String url = "jdbc:mysql://localhost:3306/database_name";

Connection connection = DriverManager.getConnection(url, username, password);
Statement statement = connection.createStatement();

String sql = "INSERT INTO table_name (field1, field2, field3) VALUES (?, ?, ?)";

while((line = reader.readLine()) != null) {
  String[] fields = line.split(",");

  PreparedStatement preparedStatement = connection.prepareStatement(sql);
  preparedStatement.setString(1, fields[0]);
  preparedStatement.setString(2, fields[1]);
  preparedStatement.setString(3, fields[2]);
  preparedStatement.executeUpdate();
}

statement.close();
connection.close();

3. 导出CSV文件

3.1 查询数据库数据

在导出CSV文件之前，我们需要从数据库中查询需要导出的数据：

String username = "root";
String password = "password";
String url = "jdbc:mysql://localhost:3306/database_name";

Connection connection = DriverManager.getConnection(url, username, password);
Statement statement = connection.createStatement();

String sql = "SELECT field1, field2, field3 FROM table_name";

ResultSet rs = statement.executeQuery(sql);

3.2 将查询结果导出为CSV文件

查询结果导出为CSV文件的过程与读取CSV文件类似，可以使用Java的I/O操作将数据写入到CSV文件中：

File file = new File("filename.csv");
PrintWriter writer = new PrintWriter(new FileWriter(file));

while (rs.next()) {
  writer.print(rs.getString("field1"));
  writer.print(",");
  writer.print(rs.getString("field2"));
  writer.print(",");
  writer.print(rs.getString("field3"));
  writer.println();
}

writer.close();

示例

示例1：从CSV文件中读取数据并导入到数据库

假设我们有一个CSV文件，其中包含用户信息，格式如下：

id,name,email
1,Alice,[e-mail]
2,Bob,[e-mail]
3,Charlie,[e-mail]

我们想要将这些用户信息导入到MySQL数据库中，具体步骤如下：

String username = "root";
String password = "password";
String url = "jdbc:mysql://localhost:3306/database_name";

Connection connection = DriverManager.getConnection(url, username, password);
Statement statement = connection.createStatement();

File file = new File("users.csv");
BufferedReader reader = new BufferedReader(new FileReader(file));
String line = "";

String sql = "INSERT INTO users (id, name, email) VALUES (?, ?, ?)";

while((line = reader.readLine()) != null) {
  String[] fields = line.split(",");

  PreparedStatement preparedStatement = connection.prepareStatement(sql);
  preparedStatement.setInt(1, Integer.parseInt(fields[0]));
  preparedStatement.setString(2, fields[1]);
  preparedStatement.setString(3, fields[2]);
  preparedStatement.executeUpdate();
}

reader.close();
statement.close();
connection.close();

示例2：从数据库中查询数据并导出为CSV文件

假设我们有一个表格users，其中包含用户信息，我们想要从users表格中查询所有用户信息并导出为CSV文件，具体步骤如下：

String username = "root";
String password = "password";
String url = "jdbc:mysql://localhost:3306/database_name";

Connection connection = DriverManager.getConnection(url, username, password);
Statement statement = connection.createStatement();

String sql = "SELECT id, name, email FROM users";

ResultSet rs = statement.executeQuery(sql);

File file = new File("users.csv");
PrintWriter writer = new PrintWriter(new FileWriter(file));

while (rs.next()) {
  writer.print(rs.getInt("id"));
  writer.print(",");
  writer.print(rs.getString("name"));
  writer.print(",");
  writer.print(rs.getString("email"));
  writer.println();
}

writer.close();
rs.close();
statement.close();
connection.close();