Servlet中操作數據庫
阿新 • • 發佈：2017-06-10
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以下內容引用自http://wiki.jikexueyuan.com/project/servlet/database-access.html：
前提先新建數據庫及插入模擬數據：
create table Employees ( id int not null, age int not null, first varchar (255), last varchar (255) ); INSERT INTO Employees VALUES (100, 18, ‘Zara‘, ‘Ali‘); INSERT INTO Employees VALUES(101, 25, ‘Mahnaz‘, ‘Fatma‘); INSERT INTO Employees VALUES (102, 30, ‘Zaid‘, ‘Khan‘); INSERT INTO Employees VALUES (103, 28, ‘Sumit‘, ‘Mittal‘);
實例：
//Loading required libraries import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; import java.sql.*; publicclass DatabaseAccess extends HttpServlet{ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // JDBC driver name and database URL final String JDBC_DRIVER="com.mysql.jdbc.Driver"; final String DB_URL="jdbc:mysql://localhost:3306/TEST?serverTimezone=UTC";// Database credentials final String USER = "root"; final String PASS = "root"; // Set response content type response.setContentType("text/html"); PrintWriter out = response.getWriter(); String title = "Database Result"; String docType = "<!doctype html public \"-//w3c//dtd html 4.0 " + "transitional//en\">\n"; out.println(docType + "<html>\n" + "<head><title>" + title + "</title></head>\n" + "<body bgcolor=\"#f0f0f0\">\n" + "<h1 align=\"center\">" + title + "</h1>\n"); Connection conn = null; Statement stmt = null; try{ // Register JDBC driver Class.forName(JDBC_DRIVER); // Open a connection conn = DriverManager.getConnection(DB_URL,USER,PASS); // Execute SQL query stmt = conn.createStatement(); String sql; sql = "SELECT id, first, last, age FROM Employees"; ResultSet rs = stmt.executeQuery(sql); // Extract data from result set while(rs.next()){ //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 out.println("ID: " + id + "<br>"); out.println(", Age: " + age + "<br>"); out.println(", First: " + first + "<br>"); out.println(", Last: " + last + "<br>"); } out.println("</body></html>"); // 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 } }
現在來編譯Servlet並在web.xml文件中創建以下條目：
<servlet> <servlet-name>DatabaseAccess</servlet-name> <servlet-class>DatabaseAccess</servlet-class> </servlet> <servlet-mapping> <servlet-name>DatabaseAccess</servlet-name> <url-pattern>/DatabaseAccess</url-pattern> </servlet-mapping>
現在使用URL http://localhost:8080/DatabaseAccess調用這個Servlet，將顯示如下所示響應：
測試工程：https://github.com/easonjim/5_java_example/tree/master/servletbasics/test10
Servlet中操作數據庫