https://github.com/developframework/expression
Easy to get value from Object, Array or Map.
https://github.com/developframework/expression
Last synced: 5 months ago
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Easy to get value from Object, Array or Map.
- Host: GitHub
- URL: https://github.com/developframework/expression
- Owner: developframework
- Created: 2017-05-06T08:06:45.000Z (about 9 years ago)
- Default Branch: master
- Last Pushed: 2022-10-09T07:12:05.000Z (over 3 years ago)
- Last Synced: 2023-07-26T21:57:04.215Z (almost 3 years ago)
- Language: Java
- Size: 74.2 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Expression说明文档
## 1. 概述
用于方便的从对象、数组、Map等结构中获取值
### 1.1. 引用
```xml
com.github.developframework
expression
${version.expression}
```
### 1.2. 依赖项
- commons-lang3.jar
- lombok.jar
## 2. 简单示例
### 2.1. 表达式对象
```java
Expression expression = Expression.parse("user.name");
```
把字符串`user.name` 解析成一个表达式对象。
可以解析的表达式字符串有：
| 表达式字符串 | 描述 |
| ---------------- | ------------------------------------------------------------ |
| `user.name` | 从根对象（根对象是对象或Map）取得user实例的name属性 |
| `users[0].name` | 从根对象（根对象是对象或Map）取得users数组实例的第1个元素的name属性 |
| `[0].name` | 从根对象（根对象是数组）取得第1个元素的name属性 |
| `user.say(name)` | 从根对象（根对象是对象或Map）调用user实例的say方法，并入参name |
| `array[0][0]` | 支持多维数组 @since 1.6.0 |
### 2.2. 取值
例如有如下结构的User实体类：
```java
@Data
public class User {
private String name;
private String[] emails;
public User(String name, String[] emails) {
this.name = name;
this.emails = emails;
}
}
```
有如下的数据结构关系：
```java
User peter = new User("Peter", new String[]{"peter@163.com", "peter@qq.com"});
User tom = new User("Tom", new String[]{"tom@163.com", "tom@qq.com"});
User[] users = new User[]{peter, tom};
Map map = new HashMap<>();
map.put("users", users);
```
说明：peter,tom两个User对象存放于users数组对象中，而users数组对象存放于map中，键值为"users"。
那么假如要从map中取得peter的第二个email值。普通java代码如下：
```java
String peterSecondEmail = ((User[])map.get("users"))[0].getMails()[1];
```
列为表达式：`users[0].emails[1]`
```java
String expressionValue = "users[0].emails[1]";
String peterSecondEmail = ExpressionUtils.getValue(map, expressionValue, String.class);
System.out.println(peterSecondEmail);
```