根据URL获取参数值得出json结果集，对外给一个接口让别人调用

背景：测试接口的时候，经常都是后端get\post请求直接返回json结果集，很想知道实现方式，虽然心中也大概了解如何实现，但还不如自己来一遍踏实！

先来看一下结果吧：

以下对一个web的get接口进行解析：

一、分层架构图：因都是老生常谈，具体不详解，我的层级分的很清楚，数据读mysql库，理论上有基础的都看得懂

二、代码展示

(1)工具类-数据源连接

package util;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

/*
 * DAO层的工具类-读取数据库文件生成实例
 */
public class ConfigManager {
	private static ConfigManager configManager;
	private static Properties properties = null;
	//构造方法私有化，用单例模式，一生成实例，就加载data.properties
	private  ConfigManager(){
		properties = new Properties();
		InputStream is = ConfigManager.class.getClassLoader().getResourceAsStream("data.properties");
		try {
			properties.load(is);
		} catch (IOException e) {
			e.printStackTrace();
		}finally{
			try {
				is.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
	//生成实例
	public static ConfigManager getInstance(){
		if(configManager==null){
			configManager = new ConfigManager();
		}
		return configManager;
	}
	//得到属性值的方法
	public static String getValue(String key){
		return properties.getProperty(key);

	}
}

ConfigManager只是为了读取data.properties文件中的各个数据源配置的值

jdbc.driver_class=com.mysql.jdbc.Driver
jdbc.connection.url=jdbc\:mysql\://127.0.0.1\:3306/test?characterEncoding\=UTF-8
jdbc.connection.username=root
jdbc.connection.password=root

package util;

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

/*
 * 基类：获取数据库连接及关闭连接、数据库增删改和查询  工具类
 * 对数据库的基本操作
 */
public class BaseDao {
	private Connection connection=null;
	private PreparedStatement pstm =null;
	private ResultSet resultset = null;
	//获取数据库连接
	public boolean getconnection(){
		boolean flag =false;
		String driver = ConfigManager.getInstance().getValue("jdbc.driver_class");
		String url =  ConfigManager.getInstance().getValue("jdbc.connection.url");
		String username =  ConfigManager.getInstance().getValue("jdbc.connection.username");
		String password =  ConfigManager.getInstance().getValue("jdbc.connection.password");
		try {
			Class.forName(driver);
			connection = DriverManager.getConnection(url, username, password);
			flag = true;
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}

		return flag;

	}
	//增、删、改操作
	public int executeUpdate(String sql,Object[] params){
		int update = 0;
		try {
			//预加载sql
			pstm = connection.prepareStatement(sql);
			for(int i=0;i<params.length;i++){
				pstm.setObject(i+1, params[i]);
			}
			update = pstm.executeUpdate();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return update;

	}
	//查询操作
	public ResultSet executeQuery(String sql,Object[] params){
		try {
			pstm = connection.prepareStatement(sql);
			for(int i=0;i<params.length;i++){
				pstm.setObject(i+1, params[i]);
			}
			resultset = pstm.executeQuery();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return resultset;

	}

	/*//模糊查询操作
		public ResultSet executeQueryLike(String sql,Object[] params){
			try {
				pstm = connection.prepareStatement(sql);
				for(int i=0;i<params.length;i++){
					pstm.setObject(i+1, "%"+params[i]+"%");
				}
				resultset = pstm.executeQuery();
			} catch (SQLException e) {
				e.printStackTrace();
			}
			return resultset;

		}*/

	//关闭连接
	public void clossconnection(){
		if(resultset!=null){
			try {
				resultset.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		if(pstm!=null){
			try {
				pstm.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		if(connection!=null){
			try {
				connection.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}
}

真正获取数据库连接，把增删除改查的方法集成工具类的，还得看BaseDao，你也可以一个java一锅炖，获取data.properties值，然后用到什么写什么

(2)dao和dao.impl

package dao;

import java.util.List;

import entity.News;

/**
 * new表实现接口
 * @author 0
 *
 */
public interface NewsDao {
	public List<News> getrows(String where);
}

----------------------------
package dao.impl;

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

import util.BaseDao;

import dao.NewsDao;
import entity.News;
/**
 * dao实现类
 * @author 0
 *
 */
public class NewsDaoImpl extends BaseDao implements NewsDao {
	@Override
	public List<News> getrows(String where) {
		 List<News> listnews=new ArrayList<News>();
		News news=null;
		String sql="select id,title,createdate,createby,url from news  where 1=1 "+where;
		Object[] params={};
		System.out.println("sql==="+sql);
		if(this.getconnection()){
			ResultSet rs = this.executeQuery(sql, params);
			try {
				while(rs.next()) {
					news = new News();
					int id = rs.getInt("id");
					String title = rs.getString("title");
					Timestamp createdate = rs.getTimestamp("createdate");
					String createby=rs.getString("createby");
					String url=rs.getString("url");
					news.setId(id);
					news.setTitle(title);
					news.setCreatedate(createdate);
					news.setCreateby(createby);
					news.setUrl(url);
					listnews.add(news);
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		return listnews;
	}

}

备注：这里要注意的是select最好写自己想要的字段，而不要写*

(3)service与service.impl

package service;

import java.util.List;

import entity.News;

public interface NewsService {
	public List<News> getrows(String where);
}

-------------------------------------------------------------
package service.impl;

import java.util.List;

import dao.NewsDao;
import dao.impl.NewsDaoImpl;

import entity.News;
import service.NewsService;

public class NewsServiceImpl implements NewsService {

	private NewsDao newsdao=new NewsDaoImpl();
	@Override
	public List<News> getrows(String where) {
		return newsdao.getrows(where);
	}

}

备注：可要可不要，我这没什么逻辑，所以可以不用。

(4)json字段

package util;

import java.util.List;

import entity.News;

/**
 * 新建分页测试类NewTotal，主要用于Json分页显示
 * @author 0
 *
 */
public class NewTotal {
	private int totle;//总数
	private List<News> rows;//新闻列表

	public NewTotal() {

	}

	public NewTotal(int totle, List<News> rows) {
		this.totle = totle;
		this.rows = rows;
	}

	public int getTotle() {
		return totle;
	}
	public void setTotle(int totle) {
		this.totle = totle;
	}
	public List<News> getRows() {
		return rows;
	}
	public void setRows(List<News> rows) {
		this.rows = rows;
	}

}

备注：其实这里的2个字段定义，就是页面中出现的2个

(5)servlet

package servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.gson.Gson;

import entity.News;

import service.NewsService;
import service.impl.NewsServiceImpl;
import util.NewTotal;

public class NewsInfoServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		NewsService newsService=new NewsServiceImpl();
		String createby=request.getParameter("createby");
		String page = request.getParameter("page");
		String pageSize=request.getParameter("pageSize");
		int pageNo=0;//页码
		int pageS=0;//页码量
		StringBuffer where=new StringBuffer();//where条件查询拼接字符串
		//判断页码值或参数存不存在
		if(page!=null &&!"".equals(page)){
			pageNo=Integer.parseInt(page);
		}else{//如果当前页码为空，则默认出第1页
			pageNo=1;
		}
		if(pageSize!=null &&!"".equals(pageSize)){
			 pageS=Integer.parseInt(pageSize);
		}else{//如果页码容量为空，则默认出一页10条
			pageS=10;
		}
		//判断创建者参数是否为空，并拼接字符串查询
		if(createby!=null &&!"".equals(createby)){
			where.append(" and createby like '%"+createby+"%'");
		}
		//如果页码值存在，页码容量不存在
		if(pageNo>0 &&(pageSize==null &&"".equals(pageSize))){
			where.append(" limit "+(pageNo-1)*10+",10");
			System.out.println("第1");
		}
		//如果页码值存在，页码容量存在：实际上完全为空的情况已经排除掉了，如果都存在肯定则可能输入默认的情况
		if(pageNo>0 && pageS>0){
			where.append(" limit "+(pageNo-1)*pageS+","+pageS);
			System.out.println("第2");
		}
		//如果页码值不存在，页码容量存在
		if((page==null &&"".equals(page)) && pageS>0 ){
			where.append(" limit 1,"+pageS);
			System.out.println("第3");
		}
		System.out.println(where.toString());
		List<News> listn=newsService.getrows(where.toString());
		int totalCount=listn.size();//总量
		//新数据封装到新闻总计类中
		NewTotal nt=new NewTotal(totalCount, listn);
		//调用Gson
		Gson gson=new Gson();
		String json=gson.toJson(nt);

		//输出到界面
		System.out.println(json);
		response.setCharacterEncoding("text/plain");
		response.setCharacterEncoding("utf-8");
		PrintWriter out =new PrintWriter(response.getOutputStream());
		out.print(json);
		out.flush();
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

备注：就这个想了一下，因为条件会比较多，各样条件，也有可能不是太充分有考虑，遇到bug再加吧~~~（我们这的开发都是这样的水平，哈哈）

(6)jsp页面与web.xml

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'index.jsp' starting page</title>
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->
  </head>

  <body>
    This is my JSP page. <br>
    <form action="getJson" method="get">
    	<!-- <input type="submit" value="点击获取新闻JSON数据"/> -->
    </form>
  </body>
</html>

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
	xmlns="http://java.sun.com/xml/ns/javaee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
	http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
  <display-name></display-name>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>NewsInfoServlet</servlet-name>
    <servlet-class>servlet.NewsInfoServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>NewsInfoServlet</servlet-name>
    <url-pattern>/newsInfoServlet</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>

  <servlet>
  	<servlet-name>JsonServlet</servlet-name>
  	<servlet-class>servlet.NewsInfoServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>JsonServlet</servlet-name>
  	<url-pattern>/getJson</url-pattern>
  </servlet-mapping>
</web-app>

其实上面这个例子非常之简单，有一段时间没有碰代码了，写起来费了点时间，不过很多都是找旧代码拷过来的。

常时间不写代码就是这么生疏！！

ps:我的servlet写的都挺顺手，但是框架不行~框架不行~框架不行~~~