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cleaning, adding comments to Database class

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This commit is contained in:
Stephan Richter
2022-04-19 08:54:43 +02:00
parent aae095f2ea
commit 95ed55fbda
3 changed files with 100 additions and 12 deletions
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2
pom.xml
View File

@@ -6,7 +6,7 @@
<groupId>org.example</groupId>
<artifactId>Widerhall</artifactId>
<version>0.0.4</version>
<version>0.0.5</version>
<build>
<plugins>
<plugin>

106
src/main/java/de/srsoftware/widerhall/data/Database.java
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@@ -21,10 +21,19 @@ public class Database {
private static Database singleton = null; // we only need one db handle ever. This will be it.
private final Connection conn; // the actual db connection handle within the singleton
/**
* This class encapsulates a compiled request.
* A compiled request is a ready-to execute sql string paired with a list of parameters
*/
public class CompiledRequest{
private final String sql;
private final List<Object> args;
/**
* create new instance
* @param sql final sql, ready to be executed
* @param args arguments for the execution of the query
*/
public CompiledRequest(String sql, List<Object> args){
this.sql = sql;
this.args = args;
@@ -95,7 +104,7 @@ public class Database {
/**
* conditions are assembled in the following form:
* SELECT … FROM … WHERE <key> in (<values>)
* SELECT … FROM … WHERE [key] in ([values])
* <values> are build as list of question marks, whose arguments are applied later
* @param args
*/
@@ -125,6 +134,10 @@ public class Database {
return clone;
}
/**
* finalize sql, save sql and arguments as compiled request
* @return
*/
public CompiledRequest compile(){
var args = new ArrayList<>();
applyValues(args);
@@ -132,6 +145,10 @@ public class Database {
return new CompiledRequest(sql.toString(),args);
}
/**
* apply values (for insert or update statements)
* @param args
*/
private void applyValues(ArrayList<Object> args){
if (values.isEmpty()) return;
var currentSql = sql();
@@ -160,11 +177,21 @@ public class Database {
}
}
/**
* set single value for a certain key
* @param key
* @param value
* @return
*/
public Request set(String key, Object value) {
values.put(key,value);
return this;
}
/**
* get the current (i.e. non-final) sql
* @return
*/
public String sql() {
return sql.toString();
}
@@ -174,34 +201,61 @@ public class Database {
return "Request("+clone().compile()+')';
}
/**
* apply a map of values (for insert/update statements)
* @param newValues
* @return
*/
public Request values(Map<String,Object> newValues) {
values.putAll(newValues);
return this;
}
/**
* add a where condition in the form of … WHERE [key] in ([values])
* @param key
* @param values
* @return
*/
public Request where(String key, Object ... values) {
for (var val : values) where(key,val);
return this;
}
/**
* add a where condition in the form of … WHERE [key] in ([values])
* @param key
* @param values
* @return
*/
public Request where(String key, Collection<? extends Object> values) {
for (var val : values) where(key,val);
return this;
}
/**
* add a where condition in the form of … WHERE [key] in ([value])
* @param key
* @param values
* @return
*/
private Request where(String key, Object value) {
var list = where.get(key);
if (list == null) where.put(key,list = new ArrayList<>());
list.add(value);
return this;
}
}
public Database(Connection connection) {
this.conn = connection;
}
/**
* take care of table creation, if required tables do not exist
* @return
* @throws SQLException
*/
private Database assertTables() throws SQLException {
if (!tableExists(User.TABLE_NAME)) User.createTable();
if (!tableExists(MailingList.TABLE_NAME)) MailingList.createTable();
@@ -209,18 +263,38 @@ public class Database {
return this;
}
/**
* prepare a deletion statement
* @param tableName
* @return
*/
public Request deleteFrom(String tableName){
return new Request(new StringBuilder("DELETE FROM ").append(tableName).append(" "));
}
/**
* prepare an insertion statement
* @param tableName
* @return
*/
public Request insertInto(String tableName){
return new Request(new StringBuilder("INSERT INTO ").append(tableName).append(" "));
}
/**
* check if we have an active db connection
* @return
*/
public boolean isOpen() {
return conn instanceof Connection;
}
/**
* Open the database, if it is not open.
* Will create the singleton on first call.
* Consecutive calls will just return the singleton.
* @return
*/
public static Database open() {
if (singleton == null){
Configuration config = Configuration.instance();
@@ -238,10 +312,22 @@ public class Database {
return singleton;
}
/**
* Create a query from a pre-set StringBuilder
* @param sql
* @return
*/
public Request query(StringBuilder sql) {
return new Request(sql);
}
/**
* create a SELECT [flields] FROM [table] request.
* If no fields are supplied, a request in the form SELECT * FROM [table] will be generated.
* @param tableName
* @param fields
* @return
*/
public Request select(String tableName,String ... fields) {
StringBuilder sql = new StringBuilder("SELECT ");
if (fields == null || fields.length == 0){
@@ -253,6 +339,12 @@ public class Database {
}
/**
* check, whether a table with the provided name exists
* @param tbName
* @return
* @throws SQLException
*/
public boolean tableExists(String tbName) throws SQLException {
try {
var sql = new StringBuilder("SELECT EXISTS (SELECT name FROM sqlite_schema WHERE type='table' AND name='")
@@ -268,12 +360,12 @@ public class Database {
}
}
/**
* create an UPDATE [tableName] query
* @param tableName
* @return
*/
public Request update(String tableName) {
return new Request(new StringBuilder("UPDATE ").append(tableName));
}
public static String xor(Object a, Object b){
// https://stackoverflow.com/a/16443025/1285585
return "(~("+a+"&"+b+"))&("+a+"|"+b+")";
}
}

4
src/test/java/de/srsoftware/widerhall/data/DatabaseTest.java
View File

@@ -54,8 +54,4 @@ public class DatabaseTest extends TestCase {
assertEquals("UPDATE Test SET x = 5",Database.open().update("Test").set("x",5).sql());
assertEquals("UPDATE Test SET x = 5, y = 6",Database.open().update("Test").set("x",5).set("y",6).sql());
}
public void testXor(){
assertEquals("(~(a&b))&(a|b)",Database.xor("a","b"));
}
}