REST API实战演练之JavaScript使用Rest API

咱们前面讲了一下如何创建REST API

假期别闲着：REST API实战演练之创建Rest API-CSDN博客

又讲了java客户端如何使用REST API

假期别闲着：REST API实战演练之客户端使用Rest API-CSDN博客

接下来咱们看看JavaScript怎么使用REST API。

一、新建一个HTML文件

二、添加几个控件元素

<body><h1>PIJON</h1><p>(Person Info in JavaScript Object Notation)</p><p><input type="text" value="Ada" id="name"><button type="button" onclick="getPersonInfo()">Get</button></p><p>Birth year:</p><input type="text" id="birthYear"><p>About:</p><textarea id="about"></textarea><p><button type="button" onclick="setPersonInfo()">Save</button></p>
</body>

三、添加一段JavaScript代码

<head>
<meta charset="UTF-8">
<title>PIJON</title><script>function getPersonInfo(){var name = document.getElementById('name').value;var ajaxRequest = new XMLHttpRequest();ajaxRequest.onreadystatechange = function(){if(ajaxRequest.readyState == 4){if(ajaxRequest.status == 200){var person = JSON.parse(ajaxRequest.responseText);document.getElementById('birthYear').value = person.birthYear;document.getElementById('about').value = person.about;}}			}ajaxRequest.open('GET', 'http://localhost:8080/HelloJSP/people/' + name);ajaxRequest.send();}function setPersonInfo(){var name = document.getElementById('name').value;var about = document.getElementById('about').value;var birthYear = document.getElementById('birthYear').value;var postData = 'name=' + name;postData += '&about=' + encodeURIComponent(about);postData += '&birthYear=' + birthYear;var ajaxRequest = new XMLHttpRequest();ajaxRequest.open('POST', 'http://localhost:8080/HelloJSP/people/' + name);ajaxRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");ajaxRequest.send(postData);}</script>
</head>

修改后完整代码如下：

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>PIJON</title><script>function getPersonInfo(){var name = document.getElementById('name').value;var ajaxRequest = new XMLHttpRequest();ajaxRequest.onreadystatechange = function(){if(ajaxRequest.readyState == 4){if(ajaxRequest.status == 200){var person = JSON.parse(ajaxRequest.responseText);document.getElementById('birthYear').value = person.birthYear;document.getElementById('about').value = person.about;}}			}ajaxRequest.open('GET', 'http://localhost:8080/HelloJSP/people/' + name);ajaxRequest.send();}function setPersonInfo(){var name = document.getElementById('name').value;var about = document.getElementById('about').value;var birthYear = document.getElementById('birthYear').value;var postData = 'name=' + name;postData += '&about=' + encodeURIComponent(about);postData += '&birthYear=' + birthYear;var ajaxRequest = new XMLHttpRequest();ajaxRequest.open('POST', 'http://localhost:8080/HelloJSP/people/' + name);ajaxRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");ajaxRequest.send(postData);}</script>
</head>
<body><h1>PIJON</h1><p>(Person Info in JavaScript Object Notation)</p><p><input type="text" value="Ada" id="name"><button type="button" onclick="getPersonInfo()">Get</button></p><p>Birth year:</p><input type="text" id="birthYear"><p>About:</p><textarea id="about"></textarea><p><button type="button" onclick="setPersonInfo()">Save</button></p>
</body>
</html>

四、启动Server确保服务端开启

五、浏览器输入访问地址

浏览器输入如下地址：

浏览器输入如下地址：http://localhost:8080/HelloJSP/TestRestAPI.html

显示如下：

六、测试rest api

点击get，获取输入人员的信息，显示如下：

我们修改一下birth year，然后点击save按钮。

保存后刷新页面，再次点击get按钮显示如下：

小结：关于XMLHttpRequest

XMLHttpRequest只是一个JavaScript对象，是一个构造函数。它一点也不神秘，它的特殊之处只在于它是由客户端（即浏览器）提供的（而不是JavaScript原生的）API
[所有现代浏览器 (IE7+、Firefox、Chrome、Safari 以及 Opera) 都内建了 XMLHttpRequest 对象]
XML对象是不断被扩展的。目前XML有两个级别：第一级提供了XMLHttpRequest对象的实现细节，第二级则进一步发展了该对象，额外添加了一些方法和属性。