question background: 
(1) using the centos7 own font, unable to display text, the installation Times New Roman to centos7 and jre/fonts also cannot display text 
(2) the tomcat catalina. Sh configured in the awt, where the environment has installed a graphical interface, background doesn't configure the awt, 
(3) don't display character, also do not report any error 

To paraphrase a verification code generation tool online, under Windows display properly: 

[code=Java] import Java. The awt. Color; 
Import the Java. The awt. The Font; 
Import the Java. The awt. Graphics; 
Import the Java. The awt. Image. BufferedImage; 
import java.util.Random; 
/* * 
* verification code generation tool 
* @ author HXL 
* 
*/
Public class CaptchaUtil {
Private BufferedImage image;//image 
Private String STR.//captcha 
Private static char code []="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ123456789". ToCharArray (); 

Public static final String SESSION_CODE_NAME="code"; 

Private CaptchaUtil () {
init();//initialization properties 
} 

/* 
* get RandomNumUtil instance 
*/

Public static CaptchaUtil Instance () {
Return new CaptchaUtil (); 
} 

/* 
* get captcha images 
*/
Public BufferedImage getImage () {
Return this. The image; 
} 

/* 
* obtain image authentication code 
*/
Public String get String () {
Return this. The STR; 
} 

Private void init () {
//in memory to create image 
Int width=85, height=20; 
BufferedImage image=new BufferedImage (width, height, BufferedImage. TYPE_INT_RGB); 
//get the graphics context 
Graphics g=image. GetGraphics (); 
//to generate random class 
Random random=new Random(); 
//set the background color in 
G.s etColor (getRandColor (200, 250)); 
G.f illRect (0, 0, width, height); 
//set the font 
G.s etFont (new Font (" Times new Roman ", the Font. PLAIN, 18)); 
//random interference lines 155, make the image of the authentication code is not easy to be detected from other programs 
G.s etColor (getRandColor (160, 200)); 
for (int i=0; i <155; I++) {
Int x=random. NextInt (width); 
Int y=random. NextInt (height); 
Int xl=random. NextInt (12); 
Int yl=random. NextInt (12); 
G.d rawLine (x, y, x + xl, y + yl); 
} 
//take random authentication code (4 digits) 
String sRand=""; 
for (int i=0; i <4. I++) {
String rand=String. The valueOf (code [random. NextInt (code. Length)]); 
SRand +=rand. 
//to display the authentication code in the image 
G.s etColor (new Color (20 + the random nextInt (110), 20 + random. NextInt (110), 20 + random. NextInt (110))); 
//function call out the color of the same, may be because the seeds too close, so can directly generate 
G.d rawString (rand, 13 * I + 6, 16); 
} 
//assignment captcha 
Enclosing the STR=sRand; 

//image effect 
G.d ispose (); 
//ByteArrayInputStream input=null; 
//ByteArrayOutputStream output=new ByteArrayOutputStream (); 
//try {
//ImageOutputStream imageOut=ImageIO. CreateImageOutputStream (output); 
//ImageIO. Write (image, "JPEG", imageOut); 
//imageOut. Close (); 
//input=new ByteArrayInputStream (output. The toByteArray ()); 
//} the catch (Exception e) {
//System. Out. Println (" captcha images the error: "+ e. oString ()); 
//} 
//this. Image=input 
This. Image=image; Assignment image/* */
} 

/* 

 * for a given range of random color*/
Fc private Color getRandColor (int, int BC) {
Random random=new Random(); 
If (fc & gt; 255) 
Fc=255; 
If (BC & gt; 255) 
BC=255; 
Int r=fc + random. NextInt (BC - fc); 
Int g=fc + random. NextInt (BC - fc); 
Int b=fc + random. NextInt (BC - fc); 
Return the new Color (r, g, b); 
} 
}