jquery+servlet实现ajax-马育民老师

# 说明

[![](https://www.malaoshi.top/upload/pic/jsp/Snipaste_2022-02-11_16-10-43.png)](https://www.malaoshi.top/upload/pic/jsp/Snipaste_2022-02-11_16-10-43.png)

# 依赖

依赖 jackson jar包：

- jackson-annotations-2.3.1.jar
- jackson-core-2.3.1.jar
- jackson-databind-2.3.1.jar

# Servlet代码

```
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;

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

import com.fasterxml.jackson.databind.ObjectMapper;

@WebServlet( urlPatterns="/testJson"  )
public class HelloLucyServlet extends HttpServlet{

@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		//一定是 text/json，否则浏览器不识别json
		resp.setContentType("text/json;charset=utf-8");
		Map map=new HashMap();
		map.put("name", "李雷");
		map.put("age", 20);
		
		ObjectMapper om=new ObjectMapper();
		String json=om.writeValueAsString(map);
		
		PrintWriter pw = resp.getWriter();
		pw.write(json);
		pw.close();//关闭
	}
}
```

### 关键代码1

必须写：

```
resp.setContentType("text/json;charset=utf-8");
```

这样浏览器的响应头才会显示 `json`，如下：

[![](https://www.malaoshi.top/upload/pic/jsp/Snipaste_2022-01-19_23-27-23.png)](https://www.malaoshi.top/upload/pic/jsp/Snipaste_2022-01-19_23-27-23.png)

这样浏览器才能识别到 `json`格式的数据

### 关键代码2

```
ObjectMapper om=new ObjectMapper();
String json=om.writeValueAsString(map);
```

其作用是将 `Map` 对象转换成 `json` 字符串

详见链接：

[Jackson 处理json（ObjectMapper）](https://www.malaoshi.top/show_1EF5rdjyd8U3.html "Jackson 处理json（ObjectMapper）")

[Jackson目录](https://www.malaoshi.top/show_1IX1uHcDmAUS.html "Jackson目录")

# html

### 引入jquery

```
<script type="text/javascript" src="js/jquery-1.11.0.min.js"></script>
```

### js代码
```
<script type="text/javascript">
$.ajax({
    url:'testJson',//请求的url
    type:'get', //请求方式，GET或POST
    data:{
        
    },
    dataType:'json',    
    success:function(data){//成功时执行该函数
        console.log(data)
    },
    error:function(xhr,textStatus){//错误时执行该函数
        alert('发生错误');
        console.log(xhr.responseJSON) // json格式，ajax请求使用该对象
    }
})
</script>
```

原文出处：/show_1IX2chMedQ9h.html