IfTag.java, IfConditionTag.java, IfThenTag.java, and IfElseTag.java, Custom tags that make use of tag nesting

IfTag.java, IfConditionTag.java, IfThenTag.java, and IfElseTag.java, Custom tags that make use of tag nesting


IfTag.java

package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
import javax.servlet.*;

/** A tag that acts like an if/then/else.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class IfTag extends TagSupport {
  private boolean condition;
  private boolean hasCondition = false;

  public void setCondition(boolean condition) {
    this.condition = condition;
    hasCondition = true;
  }

  public boolean getCondition() {
    return(condition);
  }

  public void setHasCondition(boolean flag) {
    this.hasCondition = flag;
  }

  /** Has the condition field been explicitly set? */

  public boolean hasCondition() {
    return(hasCondition);
  }

  public int doStartTag() {
    return(EVAL_BODY_INCLUDE);
  }
}


package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
import javax.servlet.*;

/** The condition part of an if tag.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class IfConditionTag extends BodyTagSupport {
  public int doStartTag() throws JspTagException {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    if (parent == null) {
      throw new JspTagException("condition not inside if");
    }
    return(EVAL_BODY_TAG);
  }

  public int doAfterBody() {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    String bodyString = getBodyContent().getString();
    if (bodyString.trim().equals("true")) {
      parent.setCondition(true);
    } else {
      parent.setCondition(false);
    }
    return(SKIP_BODY);
  }
}

package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
import javax.servlet.*;

/** The else part of an if tag.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class IfElseTag extends BodyTagSupport {
  public int doStartTag() throws JspTagException {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    if (parent == null) {
      throw new JspTagException("else not inside if");
    } else if (!parent.hasCondition()) {
      String warning =
        "condition tag must come before else tag";
      throw new JspTagException(warning);
    }
    return(EVAL_BODY_TAG);
  }

  public int doAfterBody() {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    if (!parent.getCondition()) {
      try {
        BodyContent body = getBodyContent();
        JspWriter out = body.getEnclosingWriter();
        out.print(body.getString());
      } catch(IOException ioe) {
        System.out.println("Error in IfElseTag: " + ioe);
      }
    }
    return(SKIP_BODY);
  }
}

package cwp.tags;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.*;
import javax.servlet.*;

/** The then part of an if tag.
 *  <P>
 *  Taken from Core Web Programming Java 2 Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  .
 *  May be freely used or adapted.
 */

public class IfThenTag extends BodyTagSupport {
  public int doStartTag() throws JspTagException {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    if (parent == null) {
      throw new JspTagException("then not inside if");
    } else if (!parent.hasCondition()) {
      String warning =
        "condition tag must come before then tag";
      throw new JspTagException(warning);
    }
    return(EVAL_BODY_TAG);
  }

  public int doAfterBody() {
    IfTag parent =
      (IfTag)findAncestorWithClass(this, IfTag.class);
    if (parent.getCondition()) {
      try {
        BodyContent body = getBodyContent();
        JspWriter out = body.getEnclosingWriter();
        out.print(body.getString());
      } catch(IOException ioe) {
        System.out.println("Error in IfThenTag: " + ioe);
      }
    }
    return(SKIP_BODY);
  }
}