最后看了太多的源码，为了应聘做了复习，简单地做了一个demo（反射 读取 注解 生成sql建表语句（demo））。。
二话不说，贴代码
//两个注解类，Tab用于注解实体类，Col用于注解字段或方法
package cn.zw.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
public @interface Tab {
public String name()default "";
}
package cn.zw.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD,ElementType.METHOD})
public @interface Col {
public String name()default "";
}
//被注解的实体student
package cn.zw.model;
import cn.zw.annotation.Col;
import cn.zw.annotation.Tab;
@Tab(name="t_student")
public class Student {
private Integer idCard;
@Col(name="st_age")
private Integer age;
private String name;
private String address;
public Student(){}
@Col(name="st_idCard")
public Integer getIdCard() {
return idCard;
}
public void setIdCard(Integer idCard) {
this.idCard = idCard;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Col(name="st_name")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Col(name="st_address")
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
//解析生成sql 生查询被注解的get方法，如果存在注解，就读取注解类属性，否则读取字段上的注解，如果还是没注解，就不理了。
package cn.zw.main;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import cn.zw.annotation.Col;
import cn.zw.annotation.Tab;
import cn.zw.model.Student;
public class main {
public static void main(String[] args) throws Exception {
Class cls = Student.class;
parseClass(cls);
}
public static String parseClass(Class cls) throws Exception {
//拼接建表语句
StringBuffer retSb = new StringBuffer("insert into ");
Tab tab = (Tab) cls.getAnnotation(Tab.class);
if (null != tab) {
System.out.println("在class类上注解==" + tab.name());
retSb.append(tab.name()).append(" values( ");
}else{
throw new Exception("类未被注解异常");
}
for (Method method : cls.getDeclaredMethods()) {
if (method.getName().startsWith("get")) {
Col col = method.getAnnotation(Col.class);
if (null == col) {
String fieldName = method.getName().replace("get", "");
StringBuffer sb = new StringBuffer();
for (int i = 0; i < fieldName.length(); i++) {
if (0 == i
&& Character.isUpperCase(fieldName.charAt(i))) {
sb.append(Character.toLowerCase(fieldName.charAt(i)));
} else {
sb.append(fieldName.charAt(i));
}
}
Field field = null;
try {
field = cls.getDeclaredField(sb.toString());
} catch (SecurityException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} finally {
if (null != field) {
col = field.getAnnotation(Col.class);
System.out.println("在字段上注解==" + col.name());
retSb.append(col.name()).append(",");
}
}
} else {
System.out.println("在get方法上注解==" + col.name());
retSb.append(col.name()).append(",");
}
}
}
String retStr = "";
if(retSb.toString().endsWith(",")){
retStr = retSb.toString().substring(0, retSb.toString().length()-1)+");";
}
System.out.println("建表语句==" +retStr );
return retStr;
}
}