利用JAVA反射,读取数据库表名,自动生成对应实体类的操作

本代码是利用java反射，读取数据库表自动根据表名生成实体类，数据库采用老牌SQLSERVER 2000，驱动为JTDS，其他数据库可根据情况自定修改。

代码中包含了大部分数据库类型与JAVA类型的转换，少数未包含进去的会在生成代码时打印出来，方面后期查找修改。

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
* 从数据库表反射出实体类，自动生成实体类
*
* @author Zero
*
*/
public class SqlHelper {
//基本数据配置
private String packageOutPath = "com.xxx.entity.system";// 指定实体生成所在包的路径
private String authorName = "Zero";// 作者名字
private String tablename = "xxx";// 表名
private String[] colnames; // 列名数组
private String[] colTypes; // 列名类型数组
private String version = "V0.01"; // 版本
private int[] colSizes; // 列名大小数组
private boolean f_util = false; // 是否需要导入包java.util.*
private boolean f_sql = false; // 是否需要导入包java.sql.*
private boolean f_lang = false; // 是否需要导入包java.sql.*
private String defaultPath = "/src/main/java/";
// 数据库连接
private static final String URL = "jdbc:jtds:sqlserver://192.168.29.128:1433/xxx";
private static final String NAME = "sa";
private static final String PASS = "xxx";
private static final String DRIVER = "net.sourceforge.jtds.jdbc.Driver";

/*
* 构造函数
*/
public SqlHelper() {
// 创建连接
Connection con;
// 查要生成实体类的表
String sql = "select * from " + tablename;
PreparedStatement pStemt = null;
try {
try {
Class.forName(DRIVER);
} catch (ClassNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
con = DriverManager.getConnection(URL, NAME, PASS);
pStemt = con.prepareStatement(sql);
ResultSetMetaData rsmd = pStemt.getMetaData();
int size = rsmd.getColumnCount(); // 统计列
colnames = new String[size];
colTypes = new String[size];
colSizes = new int[size];
for (int i = 0; i < size; i++) {

colnames[i] = rsmd.getColumnName(i + 1);
colTypes[i] = rsmd.getColumnTypeName(i + 1);
//自动生成包配置

// if (colTypes[i].equalsIgnoreCase("datetime")) {
// f_util = true;
// }
if (colTypes[i].equalsIgnoreCase("image") || colTypes[i].equalsIgnoreCase("text")
|| colTypes[i].equalsIgnoreCase("datetime") || colTypes[i].equalsIgnoreCase("time")
|| colTypes[i].equalsIgnoreCase("date") || colTypes[i].equalsIgnoreCase("datetime2")) {
f_sql = true;
}
// if (colTypes[i].equalsIgnoreCase("int")) {
// f_lang = true;
// }
colSizes[i] = rsmd.getColumnDisplaySize(i + 1);
}

String content = parse(colnames, colTypes, colSizes);

try {
File directory = new File("");

String path = this.getClass().getResource("").getPath();

System.out.println(path);

String outputPath = directory.getAbsolutePath() + this.defaultPath
+ this.packageOutPath.replace(".", "/") + "/" + initcap(tablename) + ".java";
System.out.println("执行完毕，生成路径为："+outputPath);
FileWriter fw = new FileWriter(outputPath);
PrintWriter pw = new PrintWriter(fw);
pw.println(content);
pw.flush();
pw.close();
} catch (IOException e) {
e.printStackTrace();
}

} catch (SQLException e) {
e.printStackTrace();
} finally {

}
}

/**
* 功能：生成实体类主体代码
*
* @param colnames
* @param colTypes
* @param colSizes
* @return
*/
private String parse(String[] colnames, String[] colTypes, int[] colSizes) {
StringBuffer sb = new StringBuffer();
// 生成package包路径
sb.append("package " + this.packageOutPath + ";\r\n");
// 判断是否导入工具包
if (f_util) {
sb.append("import java.util.Date;\r\n");
}
if (f_sql) {
sb.append("import java.sql.*;\r\n");
}
if (f_lang) {
sb.append("import java.lang.*;\r\n");
}

sb.append("\r\n");
// 注释部分
sb.append("  /**\r\n");
sb.append("  * @文件名称：" + this.tablename + ".java\r\n");
sb.append("  * @创建时间：" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()) + "\r\n");
sb.append("  * @创 建 人：" + this.authorName + " \r\n");
sb.append("  * @文件描述：" + tablename + " 实体类\r\n");
sb.append("  * @文件版本：" + this.version + " \r\n");
sb.append("  */ \r\n");
// 实体部分
sb.append("\r\n\r\npublic class " + initcap(tablename) + "{\r\n");
processAllAttrs(sb);// 属性
processAllMethod(sb);// get set方法
sb.append("}\r\n");

// System.out.println(sb.toString());
return sb.toString();
}

/**
* 功能：生成所有属性
*
* @param sb
*/
private void processAllAttrs(StringBuffer sb) {

for (int i = 0; i < colnames.length; i++) {
sb.append("\tprivate " + sqlType2JavaType(colTypes[i]) + " " + colnames[i] + ";\r\n");
}
}

/**
* 功能：生成所有方法
*
* @param sb
*/
private void processAllMethod(StringBuffer sb) {

for (int i = 0; i < colnames.length; i++) {
sb.append("\tpublic void set" + initcap(colnames[i]) + "(" + sqlType2JavaType(colTypes[i]) + " "
+ colnames[i] + "){\r\n");
sb.append("\tthis." + colnames[i] + "=" + colnames[i] + ";\r\n");
sb.append("\t}\r\n");
sb.append("\tpublic " + sqlType2JavaType(colTypes[i]) + " get" + initcap(colnames[i]) + "(){\r\n");
sb.append("\t\treturn " + colnames[i] + ";\r\n");
sb.append("\t}\r\n");
}
}

/**
* 功能：将输入字符串的首字母改成大写
*
* @param str
* @return
*/
private String initcap(String str) {

char[] ch = str.toCharArray();
if (ch[0] >= 'a' && ch[0] <= 'z') {
ch[0] = (char) (ch[0] - 32);
}

return new String(ch);
}

/**
* 功能：获得列的数据类型
*
* @param sqlType
* @return
*/
private String sqlType2JavaType(String sqlType) {

if (sqlType.equalsIgnoreCase("bit")) {
return "Boolean";
} else if (sqlType.equalsIgnoreCase("decimal") || sqlType.equalsIgnoreCase("money")
|| sqlType.equalsIgnoreCase("smallmoney") || sqlType.equalsIgnoreCase("numeric")
|| sqlType.equalsIgnoreCase("bigint")) {
return "Long";
} else if (sqlType.equalsIgnoreCase("float")) {
return "Double";
} else if (sqlType.equalsIgnoreCase("int") || sqlType.equalsIgnoreCase("int identity")) {
return "Integer";
} else if (sqlType.equalsIgnoreCase("image") || sqlType.equalsIgnoreCase("varbinary(max)")
|| sqlType.equalsIgnoreCase("varbinary") || sqlType.equalsIgnoreCase("udt")
|| sqlType.equalsIgnoreCase("timestamp") || sqlType.equalsIgnoreCase("binary")) {
return "Byte[]";
} else if (sqlType.equalsIgnoreCase("nchar") || sqlType.equalsIgnoreCase("nvarchar(max)")
|| sqlType.equalsIgnoreCase("nvarchar") || sqlType.equalsIgnoreCase("nvarchar(ntext)")
|| sqlType.equalsIgnoreCase("uniqueidentifier") || sqlType.equalsIgnoreCase("xml")
|| sqlType.equalsIgnoreCase("char") || sqlType.equalsIgnoreCase("varchar(max)")
|| sqlType.equalsIgnoreCase("text") || sqlType.equalsIgnoreCase("varchar")) {
return "String";
} else if (sqlType.equalsIgnoreCase("real")) {
return "Float";
} else if (sqlType.equalsIgnoreCase("smallint") || sqlType.equalsIgnoreCase("tinyint")) {
return "Short";
} else if (sqlType.equalsIgnoreCase("date") || sqlType.equalsIgnoreCase("datetime")
|| sqlType.equalsIgnoreCase("time") || sqlType.equalsIgnoreCase("datetime2")) {
return "Date";
} else {
System.out.println("数据类型异常，类型为：" + sqlType);
}

return null;
}

/**
* 出口 TODO
*
* @param args
*/
public static void main(String[] args) {

new SqlHelper();

}
}

补充知识：java通过反射获取类名、属性名称以及@Table注解上的表名称

我就废话不多说了，大家还是直接看代码吧~

import javax.persistence.Column;
import javax.persistence.Id;
import javax.persistence.Table;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
* @author caizw
* @createDate 2018/2/8
* @description 反射工具类
*/
public class ReflectUtils {

/**
  * 获取实体类主键
  *
  * @param clazz
  * @return
  */
 public static Field getIdField(Class<?> clazz) {
   Field[] fields = clazz.getDeclaredFields();
   Field item = null;
   for (Field field : fields) {
     Id id = field.getAnnotation(Id.class);
     if (id != null) {
       field.setAccessible(true);
       item = field;
       break;
     }
   }
   if (item == null) {
     Class<?> superclass = clazz.getSuperclass();
     if (superclass != null) {
       item = getIdField(superclass);
     }
   }
   return item;
 }

/**
  * 根据主键名称获取实体类主键属性值
  *
  * @param clazz
  * @param pkName
  * @return
  */
 public static Object getPkValueByName(Object clazz, String pkName) {
   try {
     String firstLetter = pkName.substring(0, 1).toUpperCase();
     String getter = "get" + firstLetter + pkName.substring(1);
     Method method = clazz.getClass().getMethod(getter, new Class[]{});
     Object value = method.invoke(clazz, new Object[]{});
     return value;
   } catch (Exception e) {
     return null;
   }
 }

/**
  * 通过反射将 class1不为空的值赋值给class2
  *
  * @param class1
  * @param class2
  * @throws Exception
  */
 public static void reflectClass1ToClass2(Object class1, Object class2) throws Exception {
   Field[] field = class1.getClass().getDeclaredFields();
   for (int i = 0; i < field.length; i++) {
     String name = field[i].getName();
     if ("serialVersionUID".equals(name)) {
       continue;
     }
     name = name.substring(0, 1).toUpperCase() + name.substring(1);
     Method m1 = class1.getClass().getMethod("get" + name);
     Object value = m1.invoke(class1);
     if (value != null) {
       Field f = field[i];
       f.setAccessible(true);
       f.set(class2, value);
     }
   }
 }

/**
  * 获取实体类 @Column 的其中一个属性名称
  *
  * @param clazz
  * @return
  */
 public static Map<String, String> getColumnName(Class<?> clazz) {
   Map<String, String> map = new ConcurrentHashMap<>();
   Field[] fields = clazz.getDeclaredFields();
   for (Field field : fields) {
     if (field.isAnnotationPresent(Column.class)) {
       /**
        * 获取字段名
        */
       Column declaredAnnotation = field.getDeclaredAnnotation(Column.class);
       String column = declaredAnnotation.name();
       map.put("fieldNames", field.getName());
       map.put("column", column);
       break;
     }
   }
   return map;
 }

/**
  * 通过获取类上的@Table注解获取表名称
  *
  * @param clazz
  * @return
  */
 public static Map<String, String> getTableName(Class<?> clazz) {
   Map<String, String> map = new ConcurrentHashMap<>();
   Table annotation = clazz.getAnnotation(Table.class);
   String name = annotation.name();
   String className = clazz.getSimpleName();
   map.put("tableName", name);
   map.put("className", className);
   return map;
 }
}

来源：https://blog.csdn.net/zhum_sjz/article/details/80343549