JDBC Resultset 结果集范例

JDBC ResultSet 通过移动光标的方法浏览结果集。

1. ResultSet 移动光标的方法

编号	方法	描述
1	public void beforeFirst() throws SQLException	将光标移动到第一行之前
2	public void afterLast() throws SQLException	将光标移动到最后一行之后。
3	public boolean first() throws SQLException	将光标移动到第一行。
4	public void last() throws SQLException	将光标移动到最后一行。
5	public boolean absolute(int row) throws SQLException	将光标移动到指定的行。
6	public boolean relative(int row) throws SQLException	从当前指向的位置，将光标向前或向后移动给定行数。
7	public boolean previous() throws SQLException	将光标移动到上一行。如果上一行关闭结果集，此方法返回false。
8	public boolean next() throws SQLException	将光标移动到下一行。如果结果集中没有更多行，则此方法返回false。
9	public int getRow() throws SQLException	返回光标指向的行号。
10	public void moveToInsertRow() throws SQLException	将光标移动到结果集中的特殊行，该行可用于将新行插入数据库。当前光标位置被记住。
11	public void moveToCurrentRow() throws SQLException	如果光标当前位于插入行，则将光标移回当前行; 否则，此方法什么也不做

2. ResultSet 浏览结果集范例

//STEP 1. Import required packages
import java.sql.*;

public class NavigatingResultSet {
    // JDBC driver name and database URL
    static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
    static final String DB_URL = "jdbc:mysql://localhost/EMP";

    //  Database credentials
    static final String USER = "root";
    static final String PASS = "123456";

    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try{
            //STEP 2: Register JDBC driver
            Class.forName("com.mysql.jdbc.Driver");

            //STEP 3: Open a connection
            System.out.println("Connecting to database...");
            conn = DriverManager.getConnection(DB_URL,USER,PASS);

            //STEP 4: Execute a query to create statment with
            // required arguments for RS example.
            System.out.println("Creating statement...");
            stmt = conn.createStatement(
                                ResultSet.TYPE_SCROLL_INSENSITIVE,
                                ResultSet.CONCUR_READ_ONLY);
            String sql;
            sql = "SELECT id, first, last, age FROM Employees";
            ResultSet rs = stmt.executeQuery(sql);

            // Move cursor to the last row.
            System.out.println("Moving cursor to the last...");
            rs.last();

            //STEP 5: Extract data from result set
            System.out.println("Displaying record...");
            //Retrieve by column name
            int id  = rs.getInt("id");
            int age = rs.getInt("age");
            String first = rs.getString("first");
            String last = rs.getString("last");

            //Display values
            System.out.print("ID: " + id);
            System.out.print(", Age: " + age);
            System.out.print(", First: " + first);
            System.out.println(", Last: " + last);

            // Move cursor to the first row.
            System.out.println("Moving cursor to the first row...");
            rs.first();

            //STEP 6: Extract data from result set
            System.out.println("Displaying record...");
            //Retrieve by column name
            id  = rs.getInt("id");
            age = rs.getInt("age");
            first = rs.getString("first");
            last = rs.getString("last");

            //Display values
            System.out.print("ID: " + id);
            System.out.print(", Age: " + age);
            System.out.print(", First: " + first);
            System.out.println(", Last: " + last);
            // Move cursor to the first row.

            System.out.println("Moving cursor to the next row...");
            rs.next();

            //STEP 7: Extract data from result set
            System.out.println("Displaying record...");
            id  = rs.getInt("id");
            age = rs.getInt("age");
            first = rs.getString("first");
            last = rs.getString("last");

            //Display values
            System.out.print("ID: " + id);
            System.out.print(", Age: " + age);
            System.out.print(", First: " + first);
            System.out.println(", Last: " + last);

            //STEP 8: Clean-up environment
            rs.close();
            stmt.close();
            conn.close();
        }catch(SQLException se){
            //Handle errors for JDBC
            se.printStackTrace();
        }catch(Exception e){
            //Handle errors for Class.forName
            e.printStackTrace();
        }finally{
            //finally block used to close resources
            try{
                if(stmt!=null)
                stmt.close();
            }catch(SQLException se2){
            }// nothing we can do
            try{
                if(conn!=null)
                conn.close();
            }catch(SQLException se){
                se.printStackTrace();
            }//end finally try
        }//end try
        System.out.println("Goodbye!");
    }//end main
}//end JDBCExample

3. 编译运行

F:\worksp\jdbc>javac -Djava.ext.dirs=F:\worksp\jdbc\libs NavigatingResultSet.java

F:\worksp\jdbc>java -Djava.ext.dirs=F:\worksp\jdbc\libs NavigatingResultSet

运行上面代码，得到以下结果：

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JDBC PreparedStatement 使用范例：JDBC PreparedStatement 对象扩展了 Statement 对象，给 Statement 对象增加几个高级功能。JDBC PreparedStatement 对 SQL 语句进行预编译，效率更高。另外，可以接收动态参数，避免 Statement 中的 SQL 注入问题。

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