通用分页01

一，pageBean

二，反射通用后台查询方法

三，通用的分页后台查询

四，junit4

思维导图：

一，PageBean

用来简写分页的类：分页工具类

package com.ljj.util;


public class PageBean {

	private int page = 1;// 页码

	private int rows = 10;// 页大小

	private int total = 0;// 总记录数

	private boolean pagination = true;// 是否分页

	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;
	}

	
	public int getStartIndex() {
		return (this.page - 1) * this.rows;
	}

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

}

数据库辅助类：提供了一组获得或关闭数据库对象的方法

DBAccess类：

package com.ljj.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;


public class DBAccess {
	private static String driver;
	private static String url;
	private static String user;
	private static String password;

	static {// 静态块执行一次，加载 驱动一次
		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);
		}
	}

	
	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("数据库连接(关闭)成功");
	}
}

.properties配置文件：config.properties

#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/t280?useUnicode=true&characterEncoding=UTF-8&useSSL=false
user=root
pwd=123456

中文乱码处理类：

package com.ljj.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;


public class EncodingFiter implements Filter {

	private String encoding = "UTF-8";// 默认字符集

	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;

		// 中文处理必须放到 chain.doFilter(request, response)方法前面
		res.setContentType("text/html;charset=" + this.encoding);
		if (req.getMethod().equalsIgnoreCase("post")) {
			req.setCharacterEncoding(this.encoding);
		} else {
			Map map = req.getParameterMap();// 保存所有参数名=参数值(数组)的Map集合
			Set set = map.keySet();// 取出所有参数名
			Iterator it = set.iterator();
			while (it.hasNext()) {
				String name = (String) it.next();
				String[] values = (String[]) map.get(name);// 取出参数值[注：参数值为一个数组]
				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");// 读取web.xml文件中配置的字符集
		if (null != s && !s.trim().equals("")) {
			this.encoding = s.trim();
		}
	}

}

二，反射通用后台查询

原生：

public List list(Book book,PageBean pageBean) throws Exception{
		List list  = new ArrayList();
		Connection con = DBAccess.getConnection();
		String sql = "select * from t_mvc_book where 1=1 ";
		String bname = book.getBname();
		if(StringUtils.isNotBlank(bname)) {
			sql += "and bname like '%"+bname+"%' ";
		}
		PreparedStatement pst = con.prepareStatement(sql);
		ResultSet rs = pst.executeQuery();
		while(rs.next()) {
			list.add(new Book(rs.getInt("bid"), rs.getString("bname"), rs.getFloat("price")));
		}
		return list;
	}

反射：

public List list(String sql,Class clz) throws Exception{
		List list  = new ArrayList();
		Connection con = DBAccess.getConnection();
        String sql = "select * from t_mvc_book where 1=1 ";
		String bname = book.getBname();
		if(StringUtils.isNotBlank(bname)) {
			sql += "and bname like '%"+bname+"%' ";
		}
		PreparedStatement pst = con.prepareStatement(sql);
		ResultSet rs = pst.executeQuery();
		while(rs.next()) {
//			list.add(new Book(rs.getInt("bid"), rs.getString("bname"), rs.getFloat("price")));
			T t = clz.newInstance();
			Field[] fields = clz.getDeclaredFields();
			for (Field f : fields) {
				f.setAccessible(true);
				f.set(t, rs.getObject(f.getName()));
			}
			list.add(t);
		}
		return list;
	}

三，通用的分页后台查询：

public List executeQuery(String sql,PageBean pageBean,Class clz) throws Exception{
		List list  = new ArrayList();
		Connection con = DBAccess.getConnection();
		PreparedStatement pst = null;
		ResultSet rs = null;
		
		String countSQL = getCountSQL(sql);
		String pageSQL = getPageSQL(sql,pageBean);
		
		if(pageBean != null && pageBean.isPagination()) {
			pst = con.prepareStatement(countSQL);
			rs = pst.executeQuery();
			
			if(rs.next()) {
				pageBean.setTotal(String.valueOf(rs.getObject(1)));
			}
			
			pst = con.prepareStatement(pageSQL);
			rs = pst.executeQuery();
		}else {
			pst = con.prepareStatement(sql);
			rs = pst.executeQuery();
		}
		
		
		while(rs.next()) {
//			list.add(new Book(rs.getInt("bid"), rs.getString("bname"), rs.getFloat("price")));
			T t = clz.newInstance();
			Field[] fields = clz.getDeclaredFields();
			for (Field f : fields) {
				f.setAccessible(true);
				f.set(t, rs.getObject(f.getName()));
			}
			list.add(t);
		}
		return list;
	}
 
	private String getPageSQL(String sql, PageBean pageBean) {
		return sql + " limit "+pageBean.getStartIndex()+","+pageBean.getRows();
	}
 
	private String getCountSQL(String sql) {
		return "select count(1) FROM ("+sql+") t";
	}

四，junit4

以往我们测试dao方法时需要在main方法中打印，随着方法越来越多，测试的代码也越来越繁杂，这时我们就可以使用junit4

在测试类右键后，Ctrl+n,搜索junit，选择第一个

选择junit4,并勾选setup和teardown：（运行前与运行后的方法）

再选中需要测试的dao类与dao方法：

测试类就完成了： * junit能够针对单个方法进行测试 * 相比较main而言测试耦合性降低了

测试方法：

运行结果：

分页方法测试:set显示记录数为3，显示第二页数据，应为两条

运行结果：

通用分页01

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