ResultSet结果集

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1. ResultSet结果集的引入

当我们查询数据库时，返回的是一个二维的结果集，我们这时候需要使用ResultSet来遍历结果集，获取每一行的数据。

2. 使用ResultSet遍历查询结果

boolean next()将光标从当前位置向前移一行。
String getString(int columnIndex)以Java编程语言中String的形式获取此ResultSet对象的当前行中指定列的值。
String getString(String columnLabel)以Java编程语言中String的形式获取此ResultSet对象的当前行中指定列的值。

Book.java

package com.andrew.jdbc.model;

public class Book {
    private int id;
    private String bookName;
    private float price;
    private String author;
    private int bookTypeId;
    public Book(String bookName, float price, String author, int bookTypeId) {
        super();
        this.bookName = bookName;
        this.price = price;
        this.author = author;
        this.bookTypeId = bookTypeId;
    }
    public Book(int id, String bookName, float price, String author, int bookTypeId) {
        super();
        this.id = id;
        this.bookName = bookName;
        this.price = price;
        this.author = author;
        this.bookTypeId = bookTypeId;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getBookName() {
        return bookName;
    }
    public void setBookName(String bookName) {
        this.bookName = bookName;
    }
    public float getPrice() {
        return price;
    }
    public void setPrice(float price) {
        this.price = price;
    }
    public String getAuthor() {
        return author;
    }
    public void setAuthor(String author) {
        this.author = author;
    }
    public int getBookTypeId() {
        return bookTypeId;
    }
    public void setBookTypeId(int bookTypeId) {
        this.bookTypeId = bookTypeId;
    }
    @Override
    public String toString() {
        return "["+this.id+","+this.bookName+","+this.price+","+this.author+","+this.bookTypeId+"]";
    }
}

ResultSetTest.java

package com.andrew.jdbc.chap05;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import com.andrew.jdbc.model.Book;
import com.andrew.jdbc.util.DbUtil;

public class ResultSetTest {
    private static DbUtil dbUtil = new DbUtil();
    private static void listBook() throws Exception {
        Connection connection = dbUtil.getConnection();
        String sql = "select * from t_book";
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        ResultSet resultSet = preparedStatement.executeQuery();
        while (resultSet.next()) {
            int id = resultSet.getInt(1);
            String bookName = resultSet.getString(2);
            float price = resultSet.getFloat(3);
            String author = resultSet.getString(4);
            int bookTypeId = resultSet.getInt(5);
            System.out.println("图书编号：" + id + " 图书名称：" + bookName + " 图书价格：" 
                    + price + " 图书作者：" + author + " 图书类别id：" + bookTypeId);
            System.out.println("=========================================");
        }
    }
    private static void listBook2() throws Exception {
        Connection connection = dbUtil.getConnection(); // 获取连接
        String sql = "select * from t_book";
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        ResultSet resultSet = preparedStatement.executeQuery(); // 返回结果集ResultSet
        while (resultSet.next()) {
            int id = resultSet.getInt("id");
            String bookName = resultSet.getString("bookName");
            float price = resultSet.getFloat("price");
            String author = resultSet.getString("author");
            int bookTypeId = resultSet.getInt("bookTypeId"); // 获取第五列的值 图书类别id
            System.out.println("图书编号：" + id + " 图书名称：" + bookName + " 图书价格：" 
                    + price + " 图书作者：" + author + " 图书类别id：" + bookTypeId);
            System.out.println("=========================================");

        }
    }
    private static List listBook3() throws Exception {
        List bookList = new ArrayList();
        Connection connection = dbUtil.getConnection();
        String sql = "select * from t_book";
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        ResultSet resultSet = preparedStatement.executeQuery();
        while (resultSet.next()) {
            int id = resultSet.getInt("id");
            String bookName = resultSet.getString("bookName");
            float price = resultSet.getFloat("price");
            String author = resultSet.getString("author");
            int bookTypeId = resultSet.getInt("bookTypeId");
            Book book = new Book(id, bookName, price, author, bookTypeId);
            bookList.add(book);
        }
        return bookList;
    }
    public static void main(String[] args) throws Exception {
        System.out.println("-----------------------------------");
        listBook();
        System.out.println("-----------------------------------");
        listBook2();
        System.out.println("-----------------------------------");
        List bookList = listBook3();
        for (Book book : bookList) {
            System.out.println(book);
        }
    }
}

运行结果：
-----------------------------------
图书编号：1 图书名称：java学习 图书价格：666.0 图书作者：张三 图书类别id：1
=========================================
图书编号：2 图书名称：Java修改 图书价格：666.0 图书作者：修改人2 图书类别id：1
=========================================
-----------------------------------
图书编号：1 图书名称：java学习 图书价格：666.0 图书作者：张三 图书类别id：1
=========================================
图书编号：2 图书名称：Java修改 图书价格：666.0 图书作者：修改人2 图书类别id：1
=========================================
-----------------------------------
[1,java学习,666.0,张三,1]
[2,Java修改,666.0,修改人2,1]