Predicate implementation : Predicate « Database SQL JDBC « Java

1. Java
2. Database SQL JDBC
3. Predicate

Predicate implementation

/*
JDBC Recipes: A Problem-Solution Approach (Problem-Solution Approach) (Hardcover)
by Mahmoud Parsian 


# Publisher: Apress (September 15, 2005)
# Language: English
# ISBN: 1590595203

*/

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

import javax.sql.RowSet;
import javax.sql.rowset.FilteredRowSet;
import javax.sql.rowset.Predicate;

import com.sun.rowset.FilteredRowSetImpl;

public class Main {
  public static void main(String[] args) throws Exception {
    Connection conn = getHSQLConnection();
    System.out.println("Got Connection.");
    Statement st = conn.createStatement();
    st.executeUpdate("create table survey (id int,name varchar, age int);");
    st.executeUpdate("insert into survey (id,name,age ) values (1,'nameValue', 10)");
    st.executeUpdate("insert into survey (id,name,age ) values (2,'anotherValue', 100)");

    FilteredRowSet frs = new FilteredRowSetImpl();
    frs.setUsername("sa");
    frs.setPassword("");
    frs.setUrl("jdbc:hsqldb:data/tutorial");
    frs.setCommand("SELECT id, name, age FROM survey");
    frs.execute();

    System.out.println("--- Unfiltered RowSet: ---");
    while (frs.next()) {
      System.out.println(frs.getRow() + " - " + frs.getString("id") + ":" + frs.getString("name")
          + ":" + frs.getInt("age"));
    }
    // create a filter that restricts entries in
    // the age column to be between 7 and 10
    AgeFilter filter = new AgeFilter(7, 10, 3);

    // set the filter.
    frs.beforeFirst();
    frs.setFilter(filter);

    // go to the beginning of the Rowset
    System.out.println("--- Filtered RowSet: ---");

    // show filtered data
    while (frs.next()) {
      System.out.println(frs.getRow() + " - " + frs.getString("id") + ":" + frs.getString("name")
          + ":" + frs.getInt("age"));
    }

    System.out.println("--- Try to insert new records ---");

    // Try to add an employee with age = 90 (allowed by filter)
    frs.moveToInsertRow();
    frs.updateString(1, "999");
    frs.updateString(2, "Andre");
    frs.updateInt(3, 90);
    frs.insertRow();
    frs.moveToCurrentRow();
    frs.acceptChanges();

    // try to add an survey with age = 65 (not allowed by filter)
    frs.moveToInsertRow();
    frs.updateString(1, "123");
    frs.updateString(2, "Jeff");
    frs.updateInt(3, 65);
    frs.insertRow();
    frs.moveToCurrentRow();
    frs.acceptChanges();

    // scroll to first row of rowset
    frs.beforeFirst();
    // display rows in FilteredRowset
    System.out.println("FilteredRowSet after trying to insert Jeff (age 65) and Andre (age 90):");
    while (frs.next()) {
      System.out.println(frs.getRow() + " - " + frs.getString("id") + ":" + frs.getString("name")
          + ":" + frs.getInt("age"));
    }

    frs.close();
    st.close();
    frs.close();
  }

  private static Connection getHSQLConnection() throws Exception {
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    return DriverManager.getConnection(url, "sa", "");
  }

  public static Connection getMySqlConnection() throws Exception {
    String driver = "org.gjt.mm.mysql.Driver";
    String url = "jdbc:mysql://localhost/demo2s";
    String username = "oost";
    String password = "oost";

    Class.forName(driver);
    Connection conn = DriverManager.getConnection(url, username, password);
    return conn;
  }

  public static Connection getOracleConnection() throws Exception {
    String driver = "oracle.jdbc.driver.OracleDriver";
    String url = "jdbc:oracle:thin:@localhost:1521:databaseName";
    String username = "userName";
    String password = "password";

    Class.forName(driver); // load Oracle driver
    Connection conn = DriverManager.getConnection(url, username, password);
    return conn;
  }
}

class AgeFilter implements Predicate {
  private int lowAge;

  private int highAge;

  private int columnIndex;

  private String columnName;

  public AgeFilter(int lowAge, int highAge, int columnIndex, String columnName) {
    this.lowAge = lowAge;
    this.highAge = highAge;
    this.columnName = columnName;
    this.columnIndex = columnIndex;
  }

  public AgeFilter(int lowAge, int highAge, int columnIndex) {
    this(lowAge, highAge, columnIndex, "age");
  }

  public boolean evaluate(Object value, String columnName) {
    boolean evaluation = true;
    if (columnName.equalsIgnoreCase(this.columnName)) {
      int columnValue = ((Integer) value).intValue();
      if ((columnValue >= this.lowAge) && (columnValue <= this.highAge)) {
        evaluation = true;
      } else {
        evaluation = false;
      }
    }
    return evaluation;
  }

  public boolean evaluate(Object value, int columnNumber) {
    boolean evaluation = true;
    if (columnIndex == columnNumber) {
      int columnValue = ((Integer) value).intValue();
      if ((columnValue >= this.lowAge) && (columnValue <= this.highAge)) {
        evaluation = true;
      } else {
        evaluation = false;
      }
    }
    return evaluation;
  }

  public boolean evaluate(RowSet rs) {
    if (rs == null) {
      return false;
    }

    FilteredRowSet frs = (FilteredRowSet) rs;
    boolean evaluation = false;
    try {
      int columnValue = frs.getInt(this.columnIndex);
      if ((columnValue >= this.lowAge) && (columnValue <= this.highAge)) {
        evaluation = true;
      }
    } catch (SQLException e) {
      return false;
    }
    return evaluation;
  }
}
           
       

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