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// annotations/database/TableCreator.java

// (c)2021 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

// Reflection-based annotation processor

// {java annotations.database.TableCreator

// annotations.database.Member}

package annotations.database;

import java.lang.annotation.*;

import java.lang.reflect.*;

import java.util.*;

public class TableCreator {

public static void

main(String[] args) throws Exception {

if(args.length < 1) {

System.out.println(

"arguments: annotated classes");

System.exit(0);

}

for(String className : args) {

Class<?> cl = Class.forName(className);

DBTable dbTable = cl.getAnnotation(DBTable.class);

if(dbTable == null) {

System.out.println(

"No DBTable annotations in class " +

className);

continue;

}

String tableName = dbTable.name();

// If the name is empty, use the Class name:

if(tableName.length() < 1)

tableName = cl.getName().toUpperCase();

List<String> columnDefs = new ArrayList<>();

for(Field field : cl.getDeclaredFields()) {

String columnName = null;

Annotation[] anns =

field.getDeclaredAnnotations();

if(anns.length < 1)

continue; // Not a db table column

if(anns[0] instanceof SQLInteger) {

SQLInteger sInt = (SQLInteger) anns[0];

// Use field name if name not specified

if(sInt.name().length() < 1)

columnName = field.getName().toUpperCase();

else

columnName = sInt.name();

columnDefs.add(columnName + " INT" +

getConstraints(sInt.constraints()));

}

if(anns[0] instanceof SQLString) {

SQLString sString = (SQLString) anns[0];

// Use field name if name not specified.

if(sString.name().length() < 1)

columnName = field.getName().toUpperCase();

else

columnName = sString.name();

columnDefs.add(columnName + " VARCHAR(" +

sString.value() + ")" +

getConstraints(sString.constraints()));

}

StringBuilder createCommand = new StringBuilder(

"CREATE TABLE " + tableName + "(");

for(String columnDef : columnDefs)

createCommand.append(

"\n " + columnDef + ",");

// Remove trailing comma

String tableCreate = createCommand.substring(

0, createCommand.length() - 1) + ");";

System.out.println("Table Creation SQL for " +

className + " is:\n" + tableCreate);

}

}

}

private static

String getConstraints(Constraints con) {

String constraints = "";

if(!con.allowNull())

constraints += " NOT NULL";

if(con.primaryKey())

constraints += " PRIMARY KEY";

if(con.unique())

constraints += " UNIQUE";

return constraints;

}

}

/* Output:

Table Creation SQL for annotations.database.Member is:

CREATE TABLE MEMBER(

FIRSTNAME VARCHAR(30));

Table Creation SQL for annotations.database.Member is:

CREATE TABLE MEMBER(

FIRSTNAME VARCHAR(30),

LASTNAME VARCHAR(50));

Table Creation SQL for annotations.database.Member is:

CREATE TABLE MEMBER(

FIRSTNAME VARCHAR(30),

LASTNAME VARCHAR(50),

AGE INT);

Table Creation SQL for annotations.database.Member is:

CREATE TABLE MEMBER(

FIRSTNAME VARCHAR(30),

LASTNAME VARCHAR(50),

AGE INT,

REFERENCE VARCHAR(30) PRIMARY KEY);

*/