1.JSON定义
是一种轻量级的数据交换格式
2.JSON作用
JSON 可以将 Javascript 对象中表示的一组数据转换为字符串，然后就可以在函数之间轻松地传递这个字符串，或者在异步应用程序中将字符串从 Web 客户机传递给服务器端程序。这个字符串看起来有点儿古怪，但是 Javascript 很容易解释它，而且 JSON 可以表示比"名称 / 值对"更复杂的结构。例如，可以表示数组和复杂的对象，而不仅仅是键和值的简单列表
3.为什么使用JSON
JSON采用完全独立于语言的文本格式，这些特性使JSON成为理想的数据交换语言。易于人阅读和编写，同时也易于机器解析和生成。
4.JSON语法
(0)JSON存储语法
数字（整数或浮点数）
字符串（在双引号中）
逻辑值（true 或 false）
数组（在中括号中）
对象（在大括号中）
null
(1)JSON数字(常用)
JSON 数字可以是整型或者浮点型
{ "age":30 }
(2)JSON对象(常用)
{ "name":"kgc" , "pwd":"23434" }
(3)JSON数组(常用)
[
{ "name":"菜鸟教程" , "url":"www.runoob.com" },
{ "name":"google" , "url":"www.google.com" },
{ "name":"微博" , "url":"www.weibo.com" }
]
4.JSON实战
4.1创建工程，数据库，导入jar包，js类库
4.2创建实体类
public class Fruit {
private Integer fruitId;
private String type;
private String breed;
private String area;
private String brief;
private Integer weight;
private BigDecimal price;
public Fruit() {
}
public Fruit(Integer fruitId, String type, String breed, String area, String brief, Integer weight, BigDecimal price) {
this.fruitId = fruitId;
this.type = type;
this.breed = breed;
this.area = area;
this.brief = brief;
this.weight = weight;
this.price = price;
}
public Integer getFruitId() {
return fruitId;
}
public void setFruitId(Integer fruitId) {
this.fruitId = fruitId;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getBreed() {
return breed;
}
public void setBreed(String breed) {
this.breed = breed;
}
public String getArea() {
return area;
}
public void setArea(String area) {
this.area = area;
}
public String getBrief() {
return brief;
}
public void setBrief(String brief) {
this.brief = brief;
}
public Integer getWeight() {
return weight;
}
public void setWeight(Integer weight) {
this.weight = weight;
}
public BigDecimal getPrice() {
return price;
}
public void setPrice(BigDecimal price) {
this.price = price;
}
}
4.3baseDao工具类
package cn.kgc.dao;
import java.sql.*;
public class baseDao {
// 1.定义连接对象
protected static Connection conn;
// 2.定义预编译对象
protected static PreparedStatement ps;
// 3.定义结果集对象
protected static ResultSet rs;
//4.定义连接数据库的方法getConn()
public static void getConn(){
try {
//5.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//6.管理连接
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/db_fruit","root","ok");
//7.测试连接对象
System.out.println(conn);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
//8.定义关闭连接数据库方法closeAll()
public static void closeAll(){
try {
//9.关闭结果集对象
if(rs!=null){
rs.close();
}
//10.关闭预编译对象
if(ps!=null){
ps.close();
}
//11.关闭连接对象
if(conn!=null){
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
//12.定义增删改的通用方法executeUpdate()
public int executeUpdate(String sql,Object[] params){
int flag = 0;
//13.调用连接数据库的方法
getConn();
try {
//14.调用prepareStatement(),发送sql语句给数据库
ps = conn.prepareStatement(sql);
if(params!=null){
//15.循环将方法中的参数塞入结果集中
for (int i = 0; i < params.length; i++) {
ps.setObject(i+1,params[i]);
}
}
//16.执行处理(增删改)的方法
flag = ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} finally{
closeAll();
}
return flag;
}
//17.定义通用的查询方法executeQuery()
public ResultSet executeQuery(String sql,Object[] params){
//18.连接数据库
getConn();
try {
//19.执行prepareStatement()发送sql语句到数据库
ps = conn.prepareStatement(sql);
if(params!=null){
//20.循环遍历参数，将参数塞入结果集中(所谓的?)
for (int i = 0; i < params.length; i++) {
ps.setObject(i+1,params[i]);
}
}
//21.执行处理(查询)的方法
rs = ps.executeQuery();
} catch (SQLException e) {
e.printStackTrace();
}
return rs;
}
//22.入口函数的测试
public static void main(String[] args) {
getConn();
}
}
4.4FruitDao接口
public interface FruitDao {
public List findAll();
}
4.5FuritDaoImpl实现类
public class FruitDaoImpl extends baseDao implements FruitDao{
@Override
public List findAll() {
ArrayList list = new ArrayList<>();
rs = super.executeQuery("select * from FRUIT", null);
try {
while(rs.next()){
Fruit fruit = new Fruit(rs.getInt("FRUIT_ID"), rs.getString("TYPE"),rs.getString("BREED"),rs.getString("AREA"),rs.getString("BRIEF"),rs.getInt("WEIGHT"),rs.getBigDecimal("PRICE"));
list.add(fruit);
}
} catch (SQLException e) {
e.printStackTrace();
}finally {
super.closeAll();
}
return list;
}
}
4.6FruitService接口
public interface FruitService {
public List findAll();
}
4.7FruitServiceImpl实现类
public class FruitServiceImpl implements FruitService{
private FruitDao fruitDao = new FruitDaoImpl();
@Override
public List findAll() {
return fruitDao.findAll();
}
}
4.8FruitServlet
package cn.kgc.servlet;
import cn.kgc.dao.FruitDaoImpl;
import cn.kgc.entity.Fruit;
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.serializer.SerializerFeature;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
public class FruitServlet extends HttpServlet {
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String action = request.getParameter("action");
FruitDaoImpl fruitDao = new FruitDaoImpl();
if(action.equals("list")){
List list = fruitDao.findAll();
request.setAttribute("list",list);
request.getRequestDispatcher("list.jsp").forward(request,response);
}else if(action.equals("listRspJSON")){
String json = "[{"fruitId":"11","type":"www","breed":"32323"},{"fruitId":"2","type":"zzz","breed":"dd"},{"fruitId":"3","type":"aaa","breed":"vvv"}]";
response.getWriter().print(json);
}else if(action.equals("listJSON")){
List list = fruitDao.findAll();
StringBuffer json = new StringBuffer("[");
for (int i=0;i list = fruitDao.findAll();
String json = JSON.toJSonString(list);
System.out.println(json);
response.getWriter().print(json);
}
}
}
4.82 web.ml
FruitServlet
cn.kgc.servlet.FruitServlet
FruitServlet
/FruitServlet
4.9list.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%--
Created by IntelliJ IDEA.
User: haohao
Date: 2021/11/3
Time: 12:06
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
$Title$
| 类别 |
品种 |
产地 |
总重量(公斤) |
单价(元/公斤) |
操作 |
| 类别${fruit.} |
品种 |
产地 |
总重量(公斤) |
单价(元/公斤) |
操作 |
4.10listRspJSON.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%--
Created by IntelliJ IDEA.
User: haohao
Date: 2021/11/3
Time: 12:06
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
$Title$
4.11listJson.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%--
Created by IntelliJ IDEA.
User: haohao
Date: 2021/11/3
Time: 12:06
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
$Title$
4.11 listFastJson.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%--
Created by IntelliJ IDEA.
User: haohao
Date: 2021/11/3
Time: 12:06
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
$Title$
