將jdbc結果集ResultSet轉換成物件列表
阿新 • • 發佈：2019-01-29
將jdbc結果集轉換成物件列表
估計hibernate就是用得這種方式進行轉換的。
實體物件
具體的工具類
估計hibernate就是用得這種方式進行轉換的。
實體物件
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package test;
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//實體物件，該物件的屬性與資料庫中的欄位相同，當然可以改變具體看需求
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public class Person {
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private int id;
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private int age;
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private String name;
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public int getId() {
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return id;
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}
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public void setId(int id) {
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this.id =id;
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}
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public int getAge() {
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return age;
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}
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public void setAge(int age) {
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this.age = age;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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package test;
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import java.lang.reflect.Field;
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import java.sql.Connection;
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import java.sql.PreparedStatement;
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import java.sql.ResultSet;
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import java.sql.SQLException;
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import java.util.List;
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public class Main {
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//用於測試的方法
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public static void main(String[] args) throws InstantiationException, IllegalAccessException, IllegalArgumentException, ClassNotFoundException {
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Connection conn = DbUtils.getConn();
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ResultSet rs = null;
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PreparedStatement psmt = null;
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System.out.println(conn);
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try {
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psmt = conn.prepareStatement("select
* from person");
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rs = psmt.executeQuery();
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List list = DbUtils.populate(rs, Person.class);
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for(int i = 0 ; i<list.size() ; i++){
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Person per = (Person) list.get(i);
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System.out.println("person
: id = "+per.getId()+"
name = "+per.getName()+"
age = "+per.getAge());
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}
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} catch (SQLException e) {
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e.printStackTrace();
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}finally{
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if(rs!=null){
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try {
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rs.close();
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} catch (SQLException e) {
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e.printStackTrace();
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}
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rs=null;
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}
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if(psmt!=null){
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try {
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psmt.close();
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} catch (SQLException e) {
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e.printStackTrace();
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}
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psmt=null;
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}
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if(conn!=null){
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try {
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conn.close();
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} catch (SQLException e) {
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e.printStackTrace();
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}
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conn=null;
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}
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}
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}
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具體的工具類
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package test;
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import java.lang.reflect.Field;
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import java.sql.Connection;
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import java.sql.DriverManager;
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import java.sql.ResultSet;
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import java.sql.ResultSetMetaData;
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import java.sql.SQLException;
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import java.util.ArrayList;
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import java.util.List;
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public class DbUtils {
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private static String url = "jdbc:mysql://localhost:3306/test";
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private static String username = "root";
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private static String password = "";
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private static String driverClass = "com.mysql.jdbc.Driver";
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//沒什麼好說的，獲取資料庫連線
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public static Connection getConn(){
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Connection conn = null;
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try {
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Class.forName(driverClass);
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conn = DriverManager.getConnection(url,username,password);
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} catch (ClassNotFoundException e) {
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e.printStackTrace();
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} catch (SQLException e) {
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e.printStackTrace();
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}
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return conn;
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}
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/*
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* 將rs結果轉換成物件列表
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* @param rs jdbc結果集
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* @param clazz 物件的對映類
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* return 封裝了物件的結果列表
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*/
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public static List populate(ResultSet rs , Class clazz) throws SQLException, InstantiationException, IllegalAccessException{
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//結果集的元素物件
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ResultSetMetaData rsmd = rs.getMetaData();
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//獲取結果集的元素個數
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int colCount = rsmd.getColumnCount();
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// System.out.println("#");
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// for(int i = 1;i<=colCount;i++){
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// System.out.println(rsmd.getColumnName(i));
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// System.out.println(rsmd.getColumnClassName(i));
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// System.out.println("#");
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// }
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//返回結果的列表集合
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List list = new ArrayList();
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//業務物件的屬性陣列
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Field[] fields = clazz.getDeclaredFields();
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while(rs.next()){//對每一條記錄進行操作
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Object obj = clazz.newInstance();//構造業務物件實體
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//將每一個欄位取出進行賦值
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for(int i = 1;i<=colCount;i++){
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Object value = rs.getObject(i);
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//尋找該列對應的物件屬性
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for(int j=0;j<fields.length;j++){
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Field f = fields[j];
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//如果匹配進行賦值
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if(f.getName().equalsIgnoreCase(rsmd.getColumnName(i))){
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boolean flag = f.isAccessible();
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f.setAccessible(true);
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f.set(obj, value);
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f.setAccessible(flag);
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}
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}
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}
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list.add(obj);
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}
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return list;
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}
- }