我试图在MySql dB中添加50000个数据，其中只包含2列（id，description）。但是我能够添加到30000数据但是当它试图添加更多数据时它会给我以下错误
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
at java.util.Arrays.copyOf(Unknown Source)
at java.util.Arrays.copyOf(Unknown Source)
at java.util.ArrayList.grow(Unknown Source)
at java.util.ArrayList.ensureExplicitCapacity(Unknown Source)
at java.util.ArrayList.ensureCapacityInternal(Unknown Source)
我还尝试在Run Configuration下的VM参数中添加参数。还尝试更改weblogic＆gt; bin中的setDomainEnv.cmd .Below是代码。任何可以帮助我的人::
public class SequenceGenerator {
private static final String CHAR_LIST =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
private static final int RANDOM_STRING_LENGTH = 5;
private static final String jsonFilePath ="D:/Assignments/Sequence/file.json";
static HashMap hm = new HashMap();
static Set mapSet = null;
int count=1;
/**
* This method generates random string
* and stores the values in a hashmap
*/
public void generateRandomString(){
while(count<=50000){/*Change 10000 to 30000*/
StringBuffer randStr = new StringBuffer();
for(int i=0; i<RANDOM_STRING_LENGTH; i++){
int number = getRandomNumber();
char ch = CHAR_LIST.charAt(number);
randStr.append(ch);
}
hm.put(count, randStr);
mapSet = hm.entrySet();
//System.out.println(randStr.toString());
count++;
}
}
/**
* This method generates random numbers
* @return int
*/
private int getRandomNumber() {
int randomInt = 0;
Random randomGenerator = new Random();
randomInt = randomGenerator.nextInt(CHAR_LIST.length());
if (randomInt - 1 == -1) {
return randomInt;
} else {
return randomInt - 1;
}
}
public static DataSource getMySQLDataSource() throws Exception {
Properties props = new Properties();
FileInputStream fis = null;
MysqlDataSource mysqlDS = null;
try {
fis = new FileInputStream("D:/Assignments/Sequence/db.properties");
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
props.load(fis);
mysqlDS = new MysqlDataSource();
mysqlDS.setURL(props.getProperty("MYSQL_DB_URL"));
mysqlDS.setUser(props.getProperty("MYSQL_DB_USERNAME"));
mysqlDS.setPassword(props.getProperty("MYSQL_DB_PASSWORD"));
return mysqlDS;
}
public static void main(String[] args) throws Exception
{
SequenceGenerator sg = new SequenceGenerator();
sg.generateRandomString();
System.out.println("Current size of Heap::"+Runtime.getRuntime().totalMemory());
System.out.println("Max size of Heap::"+Runtime.getRuntime().maxMemory());
Connection con = null;
Statement stmt = null;
ResultSet rs = null;
PreparedStatement pst = null;
FileWriter fw = new FileWriter(jsonFilePath);
try {
con = getMySQLDataSource().getConnection();
stmt = con.createStatement();
System.out.println("Displaying key and value pair of HashMap..");
Iterator mapIterator = mapSet.iterator();
while(mapIterator.hasNext())
{
Map.Entry mapEntry = (Map.Entry)mapIterator.next();
//int key = Integer.parseInt(mapEntry.getKey().toString());
//String value = mapEntry.getValue().toString();
pst = con.prepareStatement("insert into nodes_test values (?,?)");
pst.setInt(1, Integer.parseInt(mapEntry.getKey().toString()));
pst.setString(2, mapEntry.getValue().toString());
pst.executeUpdate();
System.out.println(Integer.parseInt(mapEntry.getKey().toString()));
}
fw.close();
} catch (SQLException e) {
e.printStackTrace();
}finally{
try {
if(rs != null) rs.close();
if(stmt != null) stmt.close();
if(pst != null) pst.close();
if(con != null) con.close();
System.out.println("Free Memory::"+Runtime.getRuntime().freeMemory());
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
答案 0 :(得分：1)
我建议在生成String后立即存储它，而不是存储在HashMap中。如果您在保存后未在应用中使用数据，则应避免使用内存。
您可以在generateRandomString（）方法中引入Connection参数，并从main（）方法传递它。创建随机字符串后，立即根据连接调用store。我也会尝试重复使用预备语句。
答案 1 :(得分：0)
首先使用以下代码找出您的堆内存
public static void main(String[]args){
long totalHeapSize = Runtime.getRuntime().totalMemory();
//Total heap size
System.out.println("Total Heap Size is: " + totalHeapSize);
}
如果使用以下环境变量
，现在更改堆大小SET _JAVA_OPTIONS = -Xms512m -Xmx1024m
或
使用以下命令
java -Xms512m -Xmx1024m TestData.java
答案 2 :(得分：0)
不要浪费记忆力。只需将生成的值直接写入数据库即可。
这是您的代码，没有不必要的内存使用。我没有做任何其他尝试来优化代码。
public class SequenceGenerator
{
private static final String CHAR_LIST =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
private static final int RANDOM_STRING_LENGTH = 5;
private static final Random RANDOM = new Random();
/**
* Generates and returns a random string
*/
public String generateRandomString() {
char[] chars = new char[RANDOM_STRING_LENGTH];
for (int i = 0; i < RANDOM_STRING_LENGTH; i++) {
int number = RANDOM.nextInt(CHAR_LIST.length());
chars[i] = CHAR_LIST.charAt(number);
}
return new String(chars);
}
public static DataSource getMySQLDataSource() throws Exception {
Properties props = new Properties();
MysqlDataSource mysqlDS = null;
FileInputStream fis = new FileInputStream(
"D:/Assignments/Sequence/db.properties");
try {
props.load(fis);
} finally {
fis.close();
}
mysqlDS = new MysqlDataSource();
mysqlDS.setURL(props.getProperty("MYSQL_DB_URL"));
mysqlDS.setUser(props.getProperty("MYSQL_DB_USERNAME"));
mysqlDS.setPassword(props.getProperty("MYSQL_DB_PASSWORD"));
return mysqlDS;
}
public static void main(String[] args) throws Exception {
SequenceGenerator sg = new SequenceGenerator();
Connection con = getMySQLDataSource().getConnection();
try {
PreparedStatement pst = con.prepareStatement("insert into nodes_test values (?,?)");
for (int i = 0; i < 50000; i++) {
pst.setInt(1, i);
pst.setString(2, sg.generateRandomString());
pst.executeUpdate();
System.out.println(i);
}
pst.close();
} finally {
con.close();
}
}
}