servlet学习总结（HOW2J.CN项目）。
项目架构 Hero.javabean包中的Hero.java是一个基础类，定义了Hero类结构中包含了哪些属性，并定义了相应的set、get方法，与MySQL表结构相同。
package bean;
public class Hero {
public int id;
public String name;
public float hp;
public int damage;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public float getHp() {
return hp;
}
public void setHp(float hp) {
this.hp = hp;
}
public int getDamage() {
return damage;
}
public void setDamage(int damage) {
this.damage = damage;
}
}
HeroDAO.java
DAO全称Data Access Object，该代码直接实现了与数据库相应操作，也可编写DAO文件接口，HraoDAO.java作为接口实现类。
package dao;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import bean.Hero;
public class HeroDAO {
public HeroDAO() {
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
public Connection getConnection() throws SQLException {
return DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8", "root",
"root");
}
public int getTotal() {
int total = 0;
try (Connection c = getConnection(); Statement s = c.createStatement();) {
String sql = "select count(*) from hero";
ResultSet rs = s.executeQuery(sql);
while (rs.next()) {
total = rs.getInt(1);
}
System.out.println("total:" + total);
} catch (SQLException e) {
e.printStackTrace();
}
return total;
}
public void add(Hero hero) {
String sql = "insert into hero values(null,?,?,?)";
try (Connection c = getConnection(); PreparedStatement ps = c.prepareStatement(sql);) {
ps.setString(1, hero.name);
ps.setFloat(2, hero.hp);
ps.setInt(3, hero.damage);
ps.execute();
ResultSet rs = ps.getGeneratedKeys();
if (rs.next()) {
int id = rs.getInt(1);
hero.id = id;
}
} catch (SQLException e) {
e.printStackTrace();
}
}
public void update(Hero hero) {
String sql = "update hero set name= ?, hp = ? , damage = ? where id = ?";
try (Connection c = getConnection(); PreparedStatement ps = c.prepareStatement(sql);) {
ps.setString(1, hero.name);
ps.setFloat(2, hero.hp);
ps.setInt(3, hero.damage);
ps.setInt(4, hero.id);
ps.execute();
} catch (SQLException e) {
e.printStackTrace();
}
}
public void delete(int id) {
try (Connection c = getConnection(); Statement s = c.createStatement();) {
String sql = "delete from hero where id = " + id;
s.execute(sql);
} catch (SQLException e) {
e.printStackTrace();
}
}
public Hero get(int id) {
Hero hero = null;
try (Connection c = getConnection(); Statement s = c.createStatement();) {
String sql = "select * from hero where id = " + id;
ResultSet rs = s.executeQuery(sql);
if (rs.next()) {
hero = new Hero();
String name = rs.getString(2);
float hp = rs.getFloat("hp");
int damage = rs.getInt(4);
hero.name = name;
hero.hp = hp;
hero.damage = damage;
hero.id = id;
}
} catch (SQLException e) {
e.printStackTrace();
}
return hero;
}
public List list() {
return list(0, Short.MAX_VALUE);
}
public List list(int start, int count) {
List heros = new ArrayList();
String sql = "select * from hero order by id desc limit ?,? ";
try (Connection c = getConnection(); PreparedStatement ps = c.prepareStatement(sql);) {
ps.setInt(1, start);
ps.setInt(2, count);
ResultSet rs = ps.executeQuery();
while (rs.next()) {
Hero hero = new Hero();
int id = rs.getInt(1);
String name = rs.getString(2);
float hp = rs.getFloat("hp");
int damage = rs.getInt(4);
hero.id = id;
hero.name = name;
hero.hp = hp;
hero.damage = damage;
heros.add(hero);
}
} catch (SQLException e) {
e.printStackTrace();
}
return heros;
}
}
HeroListServelet.java
将结果输出到前端页面中。
package servlet;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import bean.Hero;
import dao.HeroDAO;
public class HeroListServlet extends HttpServlet {
protected void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html; charset=UTF-8");
List heros = new HeroDAO().list();
StringBuffer sb = new StringBuffer();
sb.append("rn");
sb.append("id name hp damage %d %s %f %d
");
response.getWriter().write(sb.toString());
}
}
web.xml
servelt-mapping标签中存储的是url与servlet-name的映射，servlet标签中存储的是servelt-name与类的映射，最终通过url输入127.0.0.1:8080/hello，即可执行对应类结果。
#插件HelloServlet HelloServlet 10 HelloServlet /hello LoginServlet LoginServlet LoginServlet /login RegisterServlet RegisterServlet RegisterServlet /register HeroListServlet servlet.HeroListServlet HeroListServlet /listHero
引入servlet-api插件与mysql插件
#tomcat右键项目在tomcat下运行即可。
