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The way to obtain an object through the Class object is to obtain it through class.newInstance(), and instantiate an object by calling the default construction parameters.
1 /** 2 * Created by hunt on 2017/6/27. * 测试的实体类 4 * @Data 编译后会自动生成set、get、无惨构造、equals、canEqual、hashCode、toString方法 5 */ 6 @Data 7 public class Person { 8 private String name; 9 private int age;10 }
1 /** 2 * Created by hunt on 2017/6/27. 3 */ 4 public class NewInstanceTest { 5 public static void main(String[] args) { 6 Class<Person> personClass = Person.class;//获取Class实例 7 try { 8 Person p = personClass.newInstance();//通过Class获得Person实例 9 p.setAge(28);10 p.setName("hunt");11 System.out.println(p);12 } catch (InstantiationException e) {13 e.printStackTrace();14 } catch (IllegalAccessException e) {15 e.printStackTrace();16 }17 }18 }
Tip: class.newInstance() is instantiated through a parameterless constructor. An object has a parameterless constructor by default. Parametric constructor, if there is a parameterized constructor, the parameterless constructor does not exist, and a java.lang.InstantiationException exception will be thrown when the object is obtained through reflection.
1 /** 2 * Created by hunt on 2017/6/27. 3 * 测试的实体类 4 */ 5 6 public class Person { 7 private String name; 8 private int age; 9 10 public String getName() {11 return name;12 }13 14 public int getAge() {15 return age;16 }17 18 public void setName(String name) {19 this.name = name;20 }21 22 public void setAge(int age) {23 this.age = age;24 }25 26 public Person(String name,int age){}//有参数构造函数27 }
1 /** 2 * Created by hunt on 2017/6/27. 3 */ 4 public class NewInstanceTest { 5 public static void main(String[] args) { 6 Class<Person> personClass = Person.class;//获取Class实例 7 try { 8 Person p = personClass.newInstance();//通过Class获得Person实例 9 p.setAge(28);10 p.setName("hunt");11 System.out.println(p.getAge()+"----"+p.getName());12 } catch (InstantiationException e) {13 e.printStackTrace();14 } catch (IllegalAccessException e) {15 e.printStackTrace();16 } } }
Summary: When creating entity classes in the future, you must bring a no-argument constructor so that you can use reflection in the future. No exception is thrown when instantiating the object.
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