c3p0-config.xml配置檔案 完成查詢資料庫的流程
阿新 • • 發佈：2019-02-13
配置檔案
<?xml version="1.0" encoding="UTF-8"?> <c3p0-config> <!-- 預設配置，只可以出現一次 --> <default-config> <!-- 連線超時設定30秒 --> <property name="checkoutTimeout">3000</property> <!-- 30秒檢查一次connection的空閒 --> <property name="idleConnectionTestPeriod">30</property> <!--初始化的池大小 --> <property name="initialPoolSize">2</property> <!-- 最多的一個connection空閒時間 --> <property name="maxIdleTime">30</property> <!-- 最多可以有多少個連線connection --> <property name="maxPoolSize">5</property> <!-- 最少的池中有幾個連線 --> <property name="minPoolSize">2</property> <!-- 批處理的語句 --> <property name="maxStatements">50</property> <!-- 每次增長几個連線 --> <property name="acquireIncrement">3</property> <property name="driverClass">com.mysql.jdbc.Driver</property> <property name="jdbcUrl"> <![CDATA[jdbc:mysql://127.0.0.1:3306/bookstore?useUnicode=true&characterEncoding=UTF-8]]> </property> <property name="user">root</property> <property name="password">root</property> </default-config> </c3p0-config>
獲得資料庫連結
import java.sql.Connection; import javax.sql.DataSource; import com.mchange.v2.c3p0.ComboPooledDataSource; public class DataSourceUtils { private static DataSource ds; //宣告ThreadLocal容器物件 private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>(); static { ds = // 預設的讀取c3p0-config.xml中預設配置 new ComboPooledDataSource(); } public static DataSource getDatasSource() { return ds; } //提供一個返回Connection的方法 public static Connection getConn(){ Connection con = null; //先從tl中獲取資料 con = tl.get(); if(con==null){ try{ con = getDatasSource().getConnection(); //放到tl tl.set(con); }catch(Exception e){ e.printStackTrace(); } } return con; } public static void remove() { tl.remove(); } }
jsp
<td align="center" valign="top" style="width:120px;"> <a target="dataFrame" href="<c:url value='/BookServlet'/>">全部</a><br/> <c:forEach items="${types}" var="t"> <a target="dataFrame" href="<c:url value='/BookServlet?typeid=${t.id}'/>">${t.name}</a><br/> </c:forEach> </td>
BookServlet
private BookService service = new BookService();
/**
* 轉發到books.jsp
* 查詢某些圖書
*/
@Override
public void execute(HttpServletRequest req, HttpServletResponse resp)
throws Exception {
String typeid=req.getParameter("typeid");
//查詢
List<Book> list = service.query(typeid);
//封裝到req
req.setAttribute("list",list);
//轉發到books.jsp
req.getRequestDispatcher("/jsps/book/books.jsp").forward(req, resp);
} public class BookService {
private BookDao dao = new BookDao();
public List<Book> query(String typeid){
return dao.query(typeid);
}import java.util.List;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import cn.itcast.domain.Book;
import cn.itcast.utils.QueryRunner;
import static cn.itcast.utils.DataSourceUtils.*;
public class BookDao {
/**
* 查詢所有圖書
* 引數為型別id
*/
public List<Book> query(String typeid){
String sql = "select * from books";
if(typeid!=null){
sql = "select b.* from books b inner join booktype bt on b.id=bt.bookid" +
" where bt.typeid='"+typeid+"'";
}
QueryRunner run = new QueryRunner(getDatasSource());
List<Book> list = run.query(sql,new BeanListHandler<Book>(Book.class));
return list;
} QueryRunner
@Override
public <T> T query(String sql, ResultSetHandler<T> rsh){
try {
return super.query(sql, rsh);
} catch (SQLException e) {
throw new RuntimeException(e.getMessage(),e);
}
}跳轉jsp
<body style="margin-top:0px;">
以下是所有圖書<br/>
<c:forEach items="${list}" var="book">
<div>
<a href="<c:url value='/BookServlet?cmd=detail&bookid=${book.id}'/>">
<img src="<c:url value='/images/${book.img}'/>">
</a>
<br/>
${book.name}
<c:choose>
<c:when test="${book.rebate==1}">
${book.price}
</c:when>
<c:otherwise>
<font style="text-decoration: line-through;">
${book.price}
</font>
<fmt:formatNumber value="${book.price*book.rebate}" pattern="#,###.00"/>
</c:otherwise>
</c:choose>
元
</div>
</c:forEach>
</body>