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Generic paging framework

2022-06-29 09:49:00 【lion tow】

Today, I want to share a simple framework , General paging ：

Catalog

One 、 Preparation

Two 、 Test tool class Junit

3、 ... and 、Dao Method analysis and examples

One 、 Preparation

We use MySql For the database , Have some entity classes needed in the early stage ……

DBAccess：

package com.zq.util;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

/**
 *  Provides a set of methods to get or close database objects 
 * 
 */
public class DBAccess {
	private static String driver;
	private static String url;
	private static String user;
	private static String password;

	static {//  The static block executes once , load   Drive once 
		try {
			InputStream is = DBAccess.class
					.getResourceAsStream("config.properties");

			Properties properties = new Properties();
			properties.load(is);

			driver = properties.getProperty("driver");
			url = properties.getProperty("url");
			user = properties.getProperty("user");
			password = properties.getProperty("pwd");

			Class.forName(driver);
		} catch (Exception e) {
			e.printStackTrace();
			throw new RuntimeException(e);
		}
	}

	/**
	 *  Get the data connection object 
	 * 
	 * @return
	 */
	public static Connection getConnection() {
		try {
			Connection conn = DriverManager.getConnection(url, user, password);
			return conn;
		} catch (SQLException e) {
			e.printStackTrace();
			throw new RuntimeException(e);
		}
	}

	public static void close(ResultSet rs) {
		if (null != rs) {
			try {
				rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
				throw new RuntimeException(e);
			}
		}
	}

	public static void close(Statement stmt) {
		if (null != stmt) {
			try {
				stmt.close();
			} catch (SQLException e) {
				e.printStackTrace();
				throw new RuntimeException(e);
			}
		}
	}

	public static void close(Connection conn) {
		if (null != conn) {
			try {
				conn.close();
			} catch (SQLException e) {
				e.printStackTrace();
				throw new RuntimeException(e);
			}
		}
	}

	public static void close(Connection conn, Statement stmt, ResultSet rs) {
		close(rs);
		close(stmt);
		close(conn);
	}

	public static boolean isOracle() {
		return "oracle.jdbc.driver.OracleDriver".equals(driver);
	}

	public static boolean isSQLServer() {
		return "com.microsoft.sqlserver.jdbc.SQLServerDriver".equals(driver);
	}
	
	public static boolean isMysql() {
		return "com.mysql.cj.jdbc.Driver".equals(driver);
	}

	public static void main(String[] args) {
		Connection conn = DBAccess.getConnection();
		System.out.println(conn);
		DBAccess.close(conn);
		System.out.println("isOracle：" + isOracle());
		System.out.println("isSQLServer：" + isSQLServer());
		System.out.println("isMysql：" + isMysql());
		System.out.println(" Database connection ( close ) success ");
	}
}

filter ：

package com.zq.util;

import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *  Chinese scrambling 
 * 
 */
public class EncodingFiter implements Filter {

	private String encoding = "UTF-8";//  Default character set 

	public EncodingFiter() {
		super();
	}

	public void destroy() {
	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest req = (HttpServletRequest) request;
		HttpServletResponse res = (HttpServletResponse) response;

		//  Chinese processing must be put into  chain.doFilter(request, response) Method front 
		res.setContentType("text/html;charset=" + this.encoding);
		if (req.getMethod().equalsIgnoreCase("post")) {
			req.setCharacterEncoding(this.encoding);
		} else {
			Map map = req.getParameterMap();//  Save all parameter names = Parameter values ( Array ) Of Map aggregate 
			Set set = map.keySet();//  Take out all parameter names 
			Iterator it = set.iterator();
			while (it.hasNext()) {
				String name = (String) it.next();
				String[] values = (String[]) map.get(name);//  Take out the parameter value [ notes ： The parameter value is an array ]
				for (int i = 0; i < values.length; i++) {
					values[i] = new String(values[i].getBytes("ISO-8859-1"),
							this.encoding);
				}
			}
		}

		chain.doFilter(request, response);
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		String s = filterConfig.getInitParameter("encoding");//  Read web.xml The character set configured in the file 
		if (null != s && !s.trim().equals("")) {
			this.encoding = s.trim();
		}
	}

}

Paging tools ：

package com.zq.util;

/**
 *  Paging tool class 
 *
 */
public class PageBean {

	private int page = 1;//  Page number 

	private int rows = 10;//  Page size 

	private int total = 0;//  Total number of records 

	private boolean pagination = true;//  Pagination or not 

	public PageBean() {
		super();
	}

	public int getPage() {
		return page;
	}

	public void setPage(int page) {
		this.page = page;
	}

	public int getRows() {
		return rows;
	}

	public void setRows(int rows) {
		this.rows = rows;
	}

	public int getTotal() {
		return total;
	}

	public void setTotal(int total) {
		this.total = total;
	}

	public void setTotal(String total) {
		this.total = Integer.parseInt(total);
	}

	public boolean isPagination() {
		return pagination;
	}

	public void setPagination(boolean pagination) {
		this.pagination = pagination;
	}

	/**
	 *  Get the subscript of the starting record 
	 * 
	 * @return
	 */
	public int getStartIndex() {
		return (this.page - 1) * this.rows;
	}

	@Override
	public String toString() {
		return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination + "]";
	}

}

String utility class ：

package com.zq.util;

public class StringUtils {
	//  Private construction method , Protection class cannot be instantiated externally 
	private StringUtils() {
	}

	/**
	 *  If the string equals null Or the blank space is equal to "", Then return to true, Otherwise return to false
	 * 
	 * @param s
	 * @return
	 */
	public static boolean isBlank(String s) {
		boolean b = false;
		if (null == s || s.trim().equals("")) {
			b = true;
		}
		return b;
	}
	
	/**
	 *  If the string is not equal to null Or not equal to... After removing the space "", Then return to true, Otherwise return to false
	 * 
	 * @param s
	 * @return
	 */
	public static boolean isNotBlank(String s) {
		return !isBlank(s);
	}

}

The configuration file ：

#oracle9i
#driver=oracle.jdbc.driver.OracleDriver
#url=jdbc:oracle:thin:@localhost:1521:orcl
#user=scott
#pwd=123


#sql2005
#driver=com.microsoft.sqlserver.jdbc.SQLServerDriver
#url=jdbc:sqlserver://localhost:1433;DatabaseName=test1
#user=sa
#pwd=123


#sql2000
#driver=com.microsoft.jdbc.sqlserver.SQLServerDriver
#url=jdbc:microsoft:sqlserver://localhost:1433;databaseName=unit6DB
#user=sa
#pwd=888888


#mysql
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/pro?useUnicode=true&characterEncoding=UTF-8&useSSL=false
user=root
pwd=123456

Entity class Book：

package com.zq.entity;

public class Book {
	private int bid;
	private String bname;
	private float price;

	@Override
	public String toString() {
		return "Book [bid=" + bid + ", bname=" + bname + ", price=" + price + "]";
	}

	public int getBid() {
		return bid;
	}

	public void setBid(int bid) {
		this.bid = bid;
	}

	public String getBname() {
		return bname;
	}

	public void setBname(String bname) {
		this.bname = bname;
	}

	public float getPrice() {
		return price;
	}

	public void setPrice(float price) {
		this.price = price;
	}
	public Book() {
		// TODO Auto-generated constructor stub
	}

	public Book(int bid, String bname, float price) {
		super();
		this.bid = bid;
		this.bname = bname;
		this.price = price;
	}
	
	
}

Of the query Dao Method :

package com.zq.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.zq.entity.Book;
import com.zq.util.BaseDao;
import com.zq.util.CallBack;
import com.zq.util.DBAccess;
import com.zq.util.PageBean;
import com.zq.util.StringUtils;

public class BookDao extends BaseDao<Book> {
	public List<Book> list(Book book,PageBean pageBean) throws Exception{
		List<Book> list = new ArrayList<Book>();
		// Get the database connection 
		Connection con =  DBAccess.getConnection();
		// Get the execution object 
		String sql="select * from t_mvc_book where 1=1";
		String bname= book.getBname();
		if(StringUtils.isNotBlank(bname)) {
			sql+=" and bname like '%"+bname+"%'";
		}
		int bid = book.getBid();
		if(bid!=0) {
			sql+=" and bid ="+bid;
		}
		// perform sql sentence 
		PreparedStatement ps = con.prepareStatement(sql);
		ResultSet rs = ps.executeQuery();
		while(rs.next()) {
			list.add(new Book(rs.getInt(1), rs.getString(2),rs.getFloat(3)));
		}
		return list;
	}
// Additions and deletions   junit
	
	public static void main(String[] args) throws Exception {
		List<Book> list = new BookDao().list(new Book(), null);
		for (Book book : list) {
			System.out.println(book);
		}
	}
}

If we do these parts well, our foundation will be completed , The next step is to code the general page ！

Basic results ：

Two 、 Test tool class Junit

The second content I want to share with you a testing tool class , The function is to write multiple methods in a test class for alternative tests ：

① First of all, the first step is to set up when running the same package of the test , If I am here BookDao Build a Junit4, Right click the package or click the BookDao Hold down Ctrl+n

② choice Junit Text Case, Click on Next, Top choice New JUnit 4 text, Below setUp() tearDown() Choose according to your needs , Click on ok You can create a test class

③ Click here to create a test class ：

package com.zq.dao;

import static org.junit.Assert.*;

import java.util.List;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.zq.entity.Book;
import com.zq.util.PageBean;

/**
 * junit Being able to test a single method 
 *  Compare with main In terms of method , Test coupling is reduced 
 * @author  Zhang Qiang 
 *
 * 2022 year 6 month 22 The morning of 9:50:58
 */
public class BookDaoTest {

	@Before
	public void setUp() throws Exception {
		System.out.println(" Called before the tested method is tested ");
	}

	@After
	public void tearDown() throws Exception {
		System.out.println(" Called after being tested by the test method ");
	}

	@Test
	public void testList() {
		List<Book> list;
		try {
			list = new BookDao().list(new Book(), null);
			for (Book book : list) {
				System.out.println(book);
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

④ Put the code we want to test into testList() The methods of , Then you can test , The test method ： Double click the method name ——》 Right click ——》Run as

advantage ： Sure For a single method To test , Compare with main In terms of method , test The coupling is reduced

3、 ... and 、Dao Method analysis and examples

You can see that after we finish the basic code, we still have a lot of duplicate code , Now optimize the duplicate code
We create a generic class , To optimize the code BeseDao.java：

package com.zq.util;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import com.zq.entity.Book;

/**
 * T Represents an entity class    Any entity class 
 * @author  Zhang Qiang 
 *
 * 2022 year 6 month 22 The morning of 9:55:03
 */
public class BaseDao<T> {
	
	public List<T> executeQuery(String sql,PageBean pageBean ,CallBack<T> callBack) throws Exception{
		
		// Get the database connection 
		Connection con = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		
		// Splicing sql   Get the total number of records from the above ——》 Get the total number of pages 
		// Determine if pagination is needed 
		if(pageBean!= null &&pageBean.isPagination()) {
			String countSql = getCountSql(sql);
			con =  DBAccess.getConnection();
			ps = con.prepareStatement(countSql);
			rs = ps.executeQuery();
			if(rs.next()) {
				// The current entity class contains the total number of records 
				pageBean.setTotal(rs.getString("n"));
			}
			String pageSQL = getpageSql(sql,pageBean);
			con =  DBAccess.getConnection();
			ps = con.prepareStatement(pageSQL);
			rs = ps.executeQuery();
		}else {
			// No paging 
			con =  DBAccess.getConnection();
			ps = con.prepareStatement(sql);
			rs = ps.executeQuery();
		}
		/**
		 *  We query different tables , The result set is also different , What should we do ？
		 *  We pass the result set to CallBack Interface , Return a collection in the interface 
		 *  Handle... In the interface rs
		 */
		return callBack.foreach(rs);
	}
	
	/**
	 *  Assembly No N Of page data Sql
	 * @param sql
	 * @param pageBean
	 * @return
	 */
	private String getpageSql(String sql, PageBean pageBean) {
		return sql+ " limit " + pageBean.getStartIndex() +" , " +pageBean.getRows();
	}

	/**
	 *  Splicing sql sentence 
	 * @param sql  original sql sentence 
	 * @return   The last one is SQL Statement to get the total number of data 
	 */
	private String getCountSql(String sql) {
		return "select count(1) as n from ("+sql+") t";
	}
}

Here you need to implement an interface , So as to handle various calling things CallBack.java

package com.zq.util;

import java.sql.ResultSet;
import java.util.List;

/**
 *  The role of the callback function interface class 
 * 	 Who calls who deals with 
 * @author  Zhang Qiang 
 *
 * 2022 year 6 month 22 The morning of 9:56:46
 */
public interface CallBack<T> {

	List<T> foreach(ResultSet rs);
	
}

Here we can change Dao Method , Add the paged content ：

public List<Book> list2(Book book,PageBean pageBean) throws Exception{
		String sql="select * from t_mvc_book where 1=1";
		String bname= book.getBname();
		if(StringUtils.isNotBlank(bname)) {
			sql+=" and bname like '%"+bname+"%'";
		}
		int bid = book.getBid();
		if(bid!=0) {
			sql+=" and bid ="+bid;
		}
		return super.executeQuery(sql, pageBean, rs->{
			List<Book> list = new ArrayList<>();
			try {
				while(rs.next()) {
					list.add(new Book(rs.getInt("bid"), rs.getString("bname"), rs.getFloat("price")));
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
			
			return list;
		});
	}

And then OK 了 , Test it , Page the data of the second page directly ：

@Test
	public void testList3() {
		List<Book> list;
		try {
			Book b = new Book();
			PageBean pageBean =new PageBean();
			pageBean.setPage(2);
			list = new BookDao().list2(b, pageBean);
			for (Book book : list) {
				System.out.println(book);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

The result is ：