使用Spring的jdbcTemplate进一步简化JDBC操作

悠悠 2023-10-18 10:18 112阅读 0赞

先看applicationContext.xml配置文件：

<?xml version="1.0" encoding="UTF-8"?>

在看SpringUtil类

package com.r.dao;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    
    public final class SpringUtil {
    
    private static ApplicationContext  ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
    
    public static Object getBean(String beanName){
         return ctx.getBean(beanName);
    }

最后看DAO:

import java.math.BigDecimal;
    import java.util.ArrayList;
    import java.util.Iterator;
    import java.util.List;
    import java.util.Map;
    
    import org.springframework.jdbc.core.JdbcTemplate;
    
    import com.r.vo.Book;
    
    public class BookDao {
    
    private JdbcTemplate jdbcT = (JdbcTemplate) SpringUtil
            .getBean("jdbcTemplate");
    
    public List findALL() {
        String sql = "select * from BookInfo";
        return jdbcT.queryForList(sql);        
    }
    
    public List<Book> findALLBooks() {
        List<Book> books = new ArrayList<Book>();;
        String sql = "select * from BookInfo";
        List list = jdbcT.queryForList(sql); 
        Iterator iterator = list.iterator();
        Book book = null;
        while (iterator.hasNext()) {
            Map map4book = (Map) iterator.next();
            book = new Book();
            book.setBid((Integer) map4book.get("bid"));
            book.setBookName((String)map4book.get("bookName"));
            book.setBookType((String)map4book.get("bookType"));        
            book.setBookPic(((BigDecimal)map4book.get("bookPic")).doubleValue() );            
            book.setCount((Integer) map4book.get("count"));
            books.add(book);
        }
        return books;
    }    
    public int delete(int bid){
        String sql = "delete from BookInfo where bid =?";
        return jdbcT.update(sql, new Object[]{bid});
    }     
    public static void main(String[] args) {        
        List<Book> books = new BookDao().findALLBooks();;
        for(Book book:books){
            System.out.println(book.getBid()+","+book.getBookName()+","+book.getBookType());
        }
    }

细心你，会发现JdbcTemplate的实例中有一系列的方法如：queryForXXX,update,delete大大简化了JDBC操作。  
当然,还可以再进一步的优化一下,就是通过依赖注入，直接把jdbcTemplate注入到dao类的jdbcT字段。  
先看新的applicationContext.xml配置文件：

<?
    xml version="1.0" encoding="UTF-8"
    ?>
    
    
    <
    beans 
    xmlns
    ="http://www.springframework.org/schema/beans"
    
    xmlns:xsi
    ="http://www.w3.org/2001/XMLSchema-instance"
    
    xsi:schemaLocation
    ="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"

<
    bean 
    id
    ="springDSN"
    
        class
    ="org.springframework.jdbc.datasource.DriverManagerDataSource"
    >
    
        
    <
    property 
    name
    ="driverClassName"
    
            value
    ="com.microsoft.jdbc.sqlserver.SQLServerDriver"
    >
    
        
    </
    property
    >
    
        
    <
    property 
    name
    ="url"
    
            value
    ="jdbc:microsoft:sqlserver://localhost:1433;databasename=bbs"
    >
    
        
    </
    property
    >
    
        
    <
    property 
    name
    ="username"
      value
    ="sa"
    ></
    property
    >
    
        
    <
    property 
    name
    ="password"
      value
    ="sa"
    ></
    property
    >
    
    
    </
    bean
    >
    
    
    
    <
    bean 
    id
    ="jdbcTemplate"
    
        class
    ="org.springframework.jdbc.core.JdbcTemplate"
      abstract
    ="false"
    
        lazy-init
    ="false"
      autowire
    ="default"
      dependency-check
    ="default"
    >
    
        
    <
    property 
    name
    ="dataSource"
    >
    
            
    <
    ref 
    bean
    ="springDSN"
      
    />
    
        
    </
    property
    >
    
        
    </
    bean
    >
    
    
        
    <
    bean 
    id
    ="bookDao"
      class
    ="com.yy.struts.dao.BookDao"
    >
    
           
    <
    property 
    name
    ="jdbcT"
    >
    
              
    <
    ref 
    bean
    ="jdbcTemplate"
      
    />
    
           
    </
    property
    >
    
        
    </
    bean
    >
    
    
    </
    beans
    >
    
    那么新的DAO类：
    
    
    import
      java.math.BigDecimal;
    
    import
      java.util.ArrayList;
    
    import
      java.util.Iterator;
    
    import
      java.util.List;
    
    import
      java.util.Map;
    
    
    import
      org.springframework.jdbc.core.JdbcTemplate;
    
    
    import
      com.r.vo.Book;
    
    
    public
      
    class
      BookDao {
    
        
    private
      JdbcTemplate jdbcT;
    
        
    public
      List findALL() {
            String sql 
    =
      
    "
    select * from BookInfo
    "
    ;
            
    return
      jdbcT.queryForList(sql);        
        }
    
        
    public
      List
    <
    Book
    >
      findALLBooks() {
            List
    <
    Book
    >
      books 
    =
      
    new
      ArrayList
    <
    Book
    >
    ();;
            String sql 
    =
      
    "
    select * from BookInfo
    "
    ;
            List list 
    =
      jdbcT.queryForList(sql); 
            Iterator iterator 
    =
      list.iterator();
            Book book 
    =
      
    null
    ;
            
    while
      (iterator.hasNext()) {
                Map map4book 
    =
      (Map) iterator.next();
                book 
    =
      
    new
      Book();
                book.setBid((Integer) map4book.get(
    "
    bid
    "
    ));
                book.setBookName((String)map4book.get(
    "
    bookName
    "
    ));
                book.setBookType((String)map4book.get(
    "
    bookType
    "
    ));        
                book.setBookPic(((BigDecimal)map4book.get(
    "
    bookPic
    "
    )).doubleValue() );            
                book.setCount((Integer) map4book.get(
    "
    count
    "
    ));
                books.add(book);
            }
            
    return
      books;
        }    
        
    public
      
    int
      delete(
    int
      bid){
            String sql 
    =
      
    "
    delete from BookInfo where bid =?
    "
    ;
            
    return
      jdbcT.update(sql, 
    new
      Object[]{bid});
        }     
        
    public
      
    static
      
    void
      main(String[] args) {        
            List
    <
    Book
    >
      books 
    =
      
    new
      BookDao().findALLBooks();;
            
    for
    (Book book:books){
                System.out.println(book.getBid()
    +
    "
    ,
    "
    +
    book.getBookName()
    +
    "
    ,
    "
    +
    book.getBookType());
            }
        }
    }

通过依赖注入，对象之间的关系由SPRING来维护，这样能降低类与类的耦合度。