java web中的util，entity，service，servlet和Dao类有什么区别，做项目的步骤是什么

java web中的util，entity，service，servlet和Dao类有什么区别，做项目的步骤是什么Java web 项目步骤uti类，entity类，Dao类，service类，servlet类，最后写JSP前端代码显示数据uti类uti类：一般是jdbc连接数据库的代码package util;import java.sql.Connection;import java.sql.

星光灿

3545人浏览 · 2021-04-26 15:51:52

星光灿 · 2021-04-26 15:51:52 发布

java web中的util，entity，service，servlet和Dao类有什么区别，做项目的步骤是什么

Java web 项目步骤

uti类，entity类，Dao类，service类，servlet类，最后写JSP前端代码显示数据

uti类

uti类：一般是jdbc连接数据库的代码

package util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class BaseDao {
	private static String url="jdbc:mysql://localhost:3306/population_db?useUnicode=true&characterEncoding=UTF-8&useSSL=false";
	private static String userName="root";
	private static String password="123456";
	private static String driver="com.mysql.jdbc.Driver";
	private static Connection connection;
	
	static{
		try {
			Class.forName(driver);
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			System.out.println("加载失败");
		}
	}
		//获取Connection 连接对象
		public static Connection getConnection() {
			try {
				// TODO Auto-generated catch block
				if (connection == null || connection.isClosed()) {
					connection = DriverManager.getConnection(url, userName, password);
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
			return connection;
		}
		
		public static void close(Connection conn) {
			try {
				conn.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		//测试链接
		public static void main(String[] args) {
			System.out.println(getConnection());
		}
}

entity类

entity类：一般是实体类，放置get（），set（）等方法

public class Tb_population implements Serializable{
	private int id;
	private String city;
	private String community;
	private String street;
	private String name;
	private String sex;
	private String card_no;
	private String register_date;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getCity() {
		return city;
	}
	public void setCity(String city) {
		this.city = city;
	}
	public String getCommunity() {
		return community;
	}
	public void setCommunity(String community) {
		this.community = community;
	}
	public String getStreet() {
		return street;
	}
	public void setStreet(String street) {
		this.street = street;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public String getCard_no() {
		return card_no;
	}
	public void setCard_no(String card_no) {
		this.card_no = card_no;
	}
	public String getRegister_date() {
		return register_date;
	}
	public void setRegister_date(String register_date) {
		this.register_date = register_date;
	}
	@Override
	public String toString() {
		return "Tb_population [id=" + id + ", city=" + city + ", community=" + community + ", street=" + street
				+ ", name=" + name + ", sex=" + sex + ", card_no=" + card_no + ", register_date=" + register_date + "]";
	}
	public Tb_population(int id, String city, String community, String street, String name, String sex, String card_no,
			String register_date) {
		super();
		this.id = id;
		this.city = city;
		this.community = community;
		this.street = street;
		this.name = name;
		this.sex = sex;
		this.card_no = card_no;
		this.register_date = register_date;
	}
	public Tb_population() {
		super();
		// TODO Auto-generated constructor stub
	}
}

Dao类

Dao类：是数据访问层，放置数据的增删改查方法

public interface Tb_populationDAO {
	//查询
	List<Tb_population>	selectAll(String city);
	//删除
	int delTbp(int id);
	//新增
	int addTbp(Tb_population tb_population);
	//修改
	int updateTbp(Tb_population tb_population);
}

service类

service类：Service层就是服务层，对多个DAO进行再次封装，一般涉及到事务的操作

@Override
		public int delTbp(int id) {
			// TODO Auto-generated method stub
			Connection conn=null;
			try {
				//连接数据库
				conn=BaseDao.getConnection();
				//定义sql
				String sql="delete from tb_population where id="+id;
				PreparedStatement pst=conn.prepareStatement(sql);
				int resultSet=pst.executeUpdate();
				return resultSet;
			} catch (Exception e) {
				// TODO: handle exception
				e.printStackTrace();
			}finally {
				BaseDao.close(conn);
			}
			return 0;
		}

		@Override
		public int addTbp(Tb_population tb_population) {
			// TODO Auto-generated method stub
			Connection conn=null;
			try {
				//连接数据库
				conn=BaseDao.getConnection();
				//定义sql
				String sql="insert into tb_population(city,community,street,name,sex,card_no,register_date) values(?,?,?,?,?,?,?)";
				PreparedStatement pst=conn.prepareStatement(sql);
				pst.setString(1, tb_population.getCity());
				pst.setString(2, tb_population.getCommunity());
				pst.setString(3, tb_population.getStreet());
				pst.setString(4, tb_population.getName());
				pst.setString(5, tb_population.getSex());
				pst.setString(6, tb_population.getCard_no());
				pst.setString(7, tb_population.getRegister_date());
				int resultSet=pst.executeUpdate();
				return resultSet;
			} catch (Exception e) {
				// TODO: handle exception
				e.printStackTrace();
			}finally {
				BaseDao.close(conn);
			}
			return 0;
		}

		@Override
		public int updateTbp(Tb_population tb_population) {
			// TODO Auto-generated method stub
			Connection conn=null;
			try {
				//连接数据库
				conn=BaseDao.getConnection();
				//定义sql
				String sql="update tb_population set city=?,community=?,street=?,name=?,sex=?,card_no=?,register_date=? where id=?";
				PreparedStatement pst=conn.prepareStatement(sql);
				pst.setString(1, tb_population.getCity());
				pst.setString(2, tb_population.getCommunity());
				pst.setString(3, tb_population.getStreet());
				pst.setString(4, tb_population.getName());
				pst.setString(5, tb_population.getSex());
				pst.setString(6, tb_population.getCard_no());
				pst.setString(7, tb_population.getRegister_date());
				pst.setInt(8, tb_population.getId());
				int resultSet=pst.executeUpdate();
				return resultSet;
			} catch (Exception e) {
				// TODO: handle exception
				e.printStackTrace();
			}finally {
				BaseDao.close(conn);
			}
			return 0;
		}
		}

servlet类

servlet类：完成接受参数，和请求转发。调用业务，跳转到JSP页面的增删改查

查询

@WebServlet("/SelectServlet")
public class SelectServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public SelectServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doPost(request, response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		Tb_populationService populationService=new Tb_populationService();
		String city = request.getParameter("city");
		List<Tb_population> selectAll = populationService.selectAll(city);
		HttpSession session = request.getSession();
		session.setAttribute("list", selectAll);
		request.getRequestDispatcher("main.jsp").forward(request, response);
	}

}

增加

@WebServlet("/AddServlet")
public class AddServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public AddServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doPost(request, response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//取值
		String city=request.getParameter("city");
		String community=request.getParameter("community");
		String street=request.getParameter("street");
		String name=request.getParameter("name");
		String sex=request.getParameter("sex");
		String card_no=request.getParameter("card_no");
		String register_date=request.getParameter("register_date");
		Tb_population tb_population = new Tb_population();
		tb_population.setCity(city);
		tb_population.setCommunity(community);
		tb_population.setStreet(street);
		tb_population.setName(name);
		tb_population.setSex(sex);
		tb_population.setCard_no(card_no);
		tb_population.setRegister_date(register_date);
		//添加
		Tb_populationService tb_populationService = new Tb_populationService();
		int addtbp = tb_populationService.addTbp(tb_population);
		if(addtbp>0) {
			response.sendRedirect("SelectServlet");
		}
	}

}

修改

@WebServlet("/UpdateServlet")
public class UpdateServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public UpdateServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doPost(request, response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//取值，构建实体对象
		String city=request.getParameter("city");
		String community=request.getParameter("community");
		String street=request.getParameter("street");
		String name=request.getParameter("name");
		String sex=request.getParameter("sex");
		String card_no=request.getParameter("card_no");
		String register_date=request.getParameter("register_date");
		Integer id = Integer.parseInt(request.getParameter("id"));
		Tb_population tb_population = new Tb_population();
		tb_population.setCity(city);
		tb_population.setCommunity(community);
		tb_population.setStreet(street);
		tb_population.setName(name);
		tb_population.setSex(sex);
		tb_population.setCard_no(card_no);
		tb_population.setRegister_date(register_date);
		tb_population.setId(id);
		//调用接口修改
		Tb_populationService populationService=new Tb_populationService();
		int updatTbp=populationService.updateTbp(tb_population);
		//跳转回主页面
		if (updatTbp>0) {
			response.sendRedirect("SelectServlet");
			}
	}

}

删除

@WebServlet("/DelServlet")
public class DelServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DelServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doPost(request, response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//获取id
		String id = request.getParameter("id");
		Integer idInteger=Integer.parseInt(id);
		//删除
		Tb_populationService tb_populationService = new Tb_populationService();
		int delEmployee = tb_populationService.delTbp(idInteger);
		if (delEmployee>0) {
			response.sendRedirect("SelectServlet");;
		}
	}

	}