什么是Ognl
1链韭、存取對(duì)象的任意屬性，簡(jiǎn)單說(shuō)就是對(duì)javabean進(jìn)行操作(重要)
2窍株、調(diào)用對(duì)象方法民轴。
3、調(diào)用類的靜態(tài)方法
4球订、索引數(shù)組元素
5后裸、操作集合(重 要)
Ognl操作方法
操作之前必須知道如何使用OGNL表達(dá)式，并且了解OGNL表達(dá)式的取值范圍只能在其context和root中辙售，格式為
Ognl.getValue(expression,context,root);
//expression:為我們編寫(xiě)的ognl表達(dá)式轻抱，從后兩個(gè)參數(shù)中獲取值，獲取規(guī)則會(huì)從下面的例子中詳細(xì)講解
//context:ognl的上下文旦部，類型為map祈搜，
//root：ognl的根较店，可以為javabean、list容燕、map梁呈、.... 等等很多值
- 對(duì)javabean操作
package other;
import ognl.Ognl;
import ognl.OgnlException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class OgnlLearn {
public static void main(String[] args) throws Exception{
// Ognl.getValue(expression,context,root);
test1(); // 取值
test2();
test3();
test4();
test5(); // 設(shè)定值
test6();
test7(); // 其他操作
test8();
test9();
test10();
}
public static void test1() throws OgnlException {
User user = new User();
user.setName("monster");
String name = (String) Ognl.getValue("name",new HashMap(),user);
System.out.println(name);
}
public static void test2() throws OgnlException {
User user = new User();
user.setAge(2);
int name = (Integer) Ognl.getValue("age",new HashMap(),user);
System.out.println(name);
}
public static void test3() throws OgnlException {
User user = new User();
user.setPassword("123456");
String name = (String) Ognl.getValue("password",new HashMap(),user);
System.out.println(name);
}
public static void test4() throws OgnlException {
User user = new User();
Address address = new Address();
address.setCity("beijing");
address.setStreet("haidian");
user.setAddress(address);
String city = (String) Ognl.getValue("address.city",new HashMap(),user);
String street = (String) Ognl.getValue("address.street",new HashMap(),user);
System.out.println(city + "***" + street);
}
public static void test5() throws OgnlException {
User user = new User();
Ognl.getValue("name = 'monster1'",new HashMap(),user);
System.out.println(user.getName());
}
public static void test6() throws OgnlException {
User user = new User();
Address address = new Address();
address.setCity("shanghai");
user.setAddress(address);
//Ognl.getValue("address = address",new HashMap(),user);
String city = (String) Ognl.getValue("address.city",new HashMap(),user);
System.out.println(city);
}
public static void test7() throws OgnlException{
List<User> uList = new ArrayList<>();
User user1 = new User();
user1.setName("monster1");
uList.add(user1);
User user2 = new User();
user2.setName("monster2");
uList.add(user2);
System.out.println(Ognl.getValue("[0].name",new HashMap(),uList));
System.out.println(Ognl.getValue("[1].name",new HashMap(),uList));
}
public static void test8() throws OgnlException{
Map<String,String> mymap = new HashMap<>();
mymap.put("key1","value1");
mymap.put("key2","value2");
System.out.println(Ognl.getValue("key1",new HashMap(),mymap));
System.out.println(Ognl.getValue("key2",new HashMap(),mymap));
}
public static void test9() throws OgnlException{
User user = new User();
List<String> nameList = (List<String>) Ognl.getValue("{'TOM','PETER'}",new HashMap(),user);
}
public static void test10() throws OgnlException{
User user = new User();
Map<String,String> mymap = (Map<String, String>) Ognl.getValue("#{'TOM':'cat','PETER':'bigdog'}",new HashMap(),user);
}
}
user.java
package other;
public class User {
private String name;
private String password;
private int age;
private Address address;
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
address.java
package other;
public class Address {
private String city;
private String street;
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
}
- 集合操作
- 操作list集合，list結(jié)合本質(zhì)就是一個(gè)數(shù)組蘸秘，所以從list中讀取數(shù)據(jù)跟對(duì)數(shù)組的操作是一樣的官卡。
- 操作map集合
- 創(chuàng)建list集合
- 創(chuàng)建map集合
Ognl 與 Struts2 的集合
OGNL中的上下文即struts2中的actionContext
OGNL中的root即struts2中的valueStack
actionContext 與 valueStack 的關(guān)系
ActionContext：
充當(dāng)OGNL的context。是action的上下文醋虏，也可以叫做action的數(shù)據(jù)中心寻咒，本質(zhì)是一個(gè)map，在其中颈嚼，所有的數(shù)據(jù)都存放在這里毛秘，那其中到底存放了哪些東西呢，actionContext中存放數(shù)據(jù)的方式又是怎樣的阻课？
actionContext是一個(gè)map叫挟，所以其中都是以鍵值對(duì)的形式存儲(chǔ)對(duì)象，如下圖所示限煞，
request抹恳、session、application這種我們熟知的作用域署驻，注意是作用域奋献，而不是對(duì)象，
paramters：這個(gè)是表單提交的參數(shù)旺上，全部都會(huì)放到這個(gè)map中秽荞，
attr(attributes)：三個(gè)作用域所有的屬性都會(huì)放在該map下，如果有重復(fù)的抚官，那么以request域中的為準(zhǔn)。
VALUE_STACK：值棧阶捆，存放著valueStack對(duì)象凌节，也就是說(shuō)，通過(guò)ActionContext能夠獲取到valueStack洒试。
也就是說(shuō)倍奢，通過(guò)valueStack可以獲取到actionContext，通過(guò)ActionContext也可以獲取到valueStack垒棋。
valueStack是對(duì)root進(jìn)行操作卒煞，而actionContext是對(duì)context進(jìn)行操作。(root和context是OGNL中的根和上下文)
獲取值棧的方式：
ActionContext.getContext.getValueStack();//常用
ActionContext.getContext.get("VALUE_STACK");
獲取actionContext的方式
ActionContext.getContext(); //常用
valueStack.getContext();
