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类反射，用于JDBC

时间：2021-07-01 10:21:17 帮助过：11人阅读

class Student { private String name; public int age; public Student() { super(); // TODO Auto-generated constructor stub } public Student(String name, int age) { super(); this.name = name; this.age = age; } private Student(String name) { super(); this.name = name; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public String toString() { return "Student [name=" + name + ", age=" + age + "]"; } public void play() { System.out.println("play"); } public void play(String str) { System.out.println("play--"+str); } }

注意：类反射能获取公有的构造方法如果想要获取到私有的构造方法，就要使用getDeclaredConstructor,如果需要使用私有的构造方法，就要使用暴力访问constructor.setAccessible(true);

关于有参构造方法里面的参数列表怎么填，如果是字符串就String.class 如果是int型就用 int.class

Class c3 = Class.forName("com.test.reflector.Student"); //相当于获取到学生类

创建对象 Student stu = (Student) c3.newInstance(); //获取一个学生对象

获取字节码对象的无参构造 Constructor constructor = c3.getConstructor(); Student s = (Student)constructor.newInstance();

获取字节码对象的有参构造 Constructor constructor = c3.getConstructor(String.class,int.class); Student s = (Student)constructor.newInstance("张三"，“11”);

获取所有公有的构造方法 Constructor[] constructors = c3.getConstructors();

获取所有包括私有的构造方法 Constructor[] constructors = c3.getDeclaredConstructors();

通过暴力访问使用私有构造方法

Constructor constructor = c3.getDeclaredConstructor(String.class);
constructor.setAccessible(true); //设置暴力访问
Student s= (Student) constructor.newInstance("aaa"); //不设置暴力访问，编译不会出错，运行会报错

java.lang.IllegalAccessException: Class com.reflector.Demo01 can not access a member of class com.woniuxy.reflector.Student with modifiers "private"
为公有成员赋值

1 Class c1 = Class.forName("com.reflector.Student");
2 Student s= (Student) c1.newInstance();
3 Field fieldAge = c1.getField("age");
4 //给学生对象s的age字段赋值位11
5 fieldAge.set(s, 11);  //参数列表（对象，要赋的值）

为私有成员赋值

1         Student s= (Student) c1.newInstance();
2         Field fieldName = c1.getDeclaredField("name");
3         fieldName.setAccessible(true);
4         //给学生对象s的私有字段name赋值
5         fieldName.set(s, "aaa");
6         System.out.println(s);

调用无参方法

1     Class c1 = Class.forName("com.reflector.Student");
2     Student s= (Student) c1.newInstance();
3     Method method = c1.getMethod("play"); //调用学生的无参方法play
4     method.invoke(s);  //输出这个对象的方法结果

调用有参方法

1         Class c1 = Class.forName("com.reflector.Student");
2         Student s= (Student) c1.newInstance();
3         Method method = c1.getMethod("play", String.class);
4         method.invoke(s, "aaa");  //要使用的对象 ，传递的参数

类反射，用于JDBC

标签：关于 err ring Stub exception 成员变量编译出错 gen

类反射，用于JDBC

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