背景：测试接口的时候，经常都是后端getpost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~~~