Spring Architecture Series-6.Implementing JDBC Module in Spring

Introduce JDBC(Java Database Connectivity) is the standard API for database access in Java.However,working with JDBC can be tedious and error-prone.In this article,i"ll explore how to implement a JDBC module that simplifies database operations, based on my miniSpring project's implementation. Core Components The JDBC module consists of several key components: src/com/yaruyng/jdbc/ ├── core/ │ ├── JdbcTemplate.java │ ├── RowMapper.java │ ├── ResultSetExtractor.java │ ├── StatementCallBack.java │ ├── PreparedStatementCallBack.java │ └── ArgumentPreparedStatementSetter.java ├── datasource/ └── pool/ JdbcTemplate:The Core Class The JdbcTemplate class is the central component that simplifies JDBC operations: public class JdbcTemplate { private DataSource dataSource; public Object query(StatementCallBack stmtCallBack) { Connection con = null; Statement stmt = null; try { con = dataSource.getConnection(); stmt = con.createStatement(); return stmtCallBack.doInStatement(stmt); } catch (SQLException e) { e.printStackTrace(); } finally { try { stmt.close(); con.close(); } catch (SQLException e) { } } return null; } public Object query(String sql, Object[] args, PreparedStatementCallBack pstmtCallBack) { Connection con = null; PreparedStatement pstmt = null; try { con = dataSource.getConnection(); pstmt = con.prepareStatement(sql); ArgumentPreparedStatementSetter setter = new ArgumentPreparedStatementSetter(args); setter.setValues(pstmt); return pstmtCallBack.doInPreparedStatement(pstmt); } catch (SQLException e) { throw new RuntimeException(e); } finally { try { pstmt.close(); con.close(); } catch (SQLException e) { } } } } Key features: Resource management Exception handing Connection pooling support Prepared statement support Row Mapping The RowMapper interface provides a flexible way to map database rows to objects: public interface RowMapper { T mapRow(ResultSet rs, int rowNum) throws SQLException; } Usage example public class UserRowMapper implements RowMapper { @Override public User mapRow(ResultSet rs, int rowNum) throws SQLException { User user = new User(); user.setId(rs.getInt("id")); user.setName(rs.getString("name")); user.setEmail(rs.getString("email")); return user; } } Parameter Handling The ArgumentPreparedStatementSetter class handles parameter binding: public class ArgumentPreparedStatementSetter { private final Object[] args; public void setValues(PreparedStatement pstmt) throws SQLException { if (this.args != null) { for (int i = 0; i

Mar 27, 2025 - 04:46

Spring Architecture Series-6.Implementing JDBC Module in Spring

Introduce

JDBC(Java Database Connectivity) is the standard API for database access in Java.However,working with JDBC can be tedious and error-prone.In this article,i"ll explore how to implement a JDBC module that simplifies database operations, based on my miniSpring project's implementation.

Core Components

The JDBC module consists of several key components:

src/com/yaruyng/jdbc/
├── core/
│   ├── JdbcTemplate.java
│   ├── RowMapper.java
│   ├── ResultSetExtractor.java
│   ├── StatementCallBack.java
│   ├── PreparedStatementCallBack.java
│   └── ArgumentPreparedStatementSetter.java
├── datasource/
└── pool/

JdbcTemplate:The Core Class

The JdbcTemplate class is the central component that simplifies JDBC operations:

public class JdbcTemplate {
  private DataSource dataSource;

  public Object query(StatementCallBack stmtCallBack) {
    Connection con = null;
    Statement stmt = null;
    try {
      con = dataSource.getConnection();
      stmt = con.createStatement();
      return stmtCallBack.doInStatement(stmt);
    } catch (SQLException e) {
      e.printStackTrace();
    } finally {
      try {
        stmt.close();
        con.close();
      } catch (SQLException e) {
      }
    }
    return null;
  }

  public Object query(String sql, Object[] args,
                      PreparedStatementCallBack pstmtCallBack) {
    Connection con = null;
    PreparedStatement pstmt = null;
    try {
      con = dataSource.getConnection();
      pstmt = con.prepareStatement(sql);
      ArgumentPreparedStatementSetter setter =
        new ArgumentPreparedStatementSetter(args);
      setter.setValues(pstmt);
      return pstmtCallBack.doInPreparedStatement(pstmt);
    } catch (SQLException e) {
      throw new RuntimeException(e);
    } finally {
      try {
        pstmt.close();
        con.close();
      } catch (SQLException e) {
      }
    }
  }
}

Key features:

Resource management
Exception handing
Connection pooling support
Prepared statement support

Row Mapping

The RowMapper interface provides a flexible way to map database rows to objects:

public interface RowMapper<T> {
    T mapRow(ResultSet rs, int rowNum) throws SQLException;
}

Usage example

public class UserRowMapper implements RowMapper<User> {
    @Override
    public User mapRow(ResultSet rs, int rowNum) throws SQLException {
        User user = new User();
        user.setId(rs.getInt("id"));
        user.setName(rs.getString("name"));
        user.setEmail(rs.getString("email"));
        return user;
    }
}

Parameter Handling

The ArgumentPreparedStatementSetter class handles parameter binding:

public class ArgumentPreparedStatementSetter {
    private final Object[] args;

    public void setValues(PreparedStatement pstmt) throws SQLException {
        if (this.args != null) {
            for (int i = 0; i < this.args.length; i++) {
                Object arg = this.args[i];
                doSetValue(pstmt, i+1, arg);
            }
        }
    }

    private void doSetValue(PreparedStatement pstmt, 
            int parameterPosition, Object argValue) throws SQLException {
        if (argValue instanceof String) {
            pstmt.setString(parameterPosition, (String)argValue);
        }
        else if (argValue instanceof Integer) {
            pstmt.setInt(parameterPosition, (int)argValue);
        }
        else if (argValue instanceof java.util.Date) {
            pstmt.setDate(parameterPosition, 
                new java.sql.Date(((java.util.Date)argValue).getTime()));
        }
    }
}

Features:

Type-safe parameter binding
Support for common data types
Extensible design

Result Set Extraction

The ResultSetExtractor interface provides a way to process result sets:

public interface ResultSetExtractor<T> {
  T extractData(ResultSet rs) throws SQLException;
}

Implementation example:

public class RowMapperResultSetExtractor<T> implements ResultSetExtractor<List<T>> {
    private final RowMapper<T> rowMapper;

    public RowMapperResultSetExtractor(RowMapper<T> rowMapper) {
        this.rowMapper = rowMapper;
    }

    @Override
    public List<T> extractData(ResultSet rs) throws SQLException {
        List<T> results = new ArrayList<>();
        int rowNum = 0;
        while (rs.next()) {
            results.add(rowMapper.mapRow(rs, ++rowNum));
        }
        return results;
    }
}

Usage Example

1. Simple Query

List<User> users = jdbcTemplate.query(
    "SELECT * FROM users WHERE age > ?",
    new Object[]{18},
    new UserRowMapper()
);

2. Custom Statement Processing

Object result = jdbcTemplate.query(new StatementCallBack() {
    @Override
    public Object doInStatement(Statement stmt) throws SQLException {
        ResultSet rs = stmt.executeQuery("SELECT COUNT(*) FROM users");
        if (rs.next()) {
            return rs.getInt(1);
        }
        return 0;
    }
});

3. Prepared Statement with Callback

Object result = jdbcTemplate.query(
    "UPDATE users SET name = ? WHERE id = ?",
    new Object[]{"John", 1},
    new PreparedStatementCallBack() {
        @Override
        public Object doInPreparedStatement(PreparedStatement pstmt) 
                throws SQLException {
            return pstmt.executeUpdate();
        }
    }
);